What changed in this filing

/stocks — the workspaceLOADING

Item 9A. Controls and Procedures

2024-03-21 compared with 2023-03-16 · 359 added, 292 removed, 539 unchanged (55% of the section changed)

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Evaluation of Disclosure Controls and Procedures

The Company has established disclosure controls and procedures (as defined in Rules 13a-15(e) and 15d-15(e) under the Exchange Act) designed to ensure that information required to be disclosed in the reports that the Company files or submits under the Securities Exchange Act of 1934, as amended, or Exchange Act, is recorded, processed, summarized and reported within the time periods specified in the SEC’s rules and forms and is accumulated and communicated to management, including the principal executive officer (our Chief Executive Officer) and principal financial officer (our Chief Financial Officer), to allow timely decisions regarding required disclosure.

In addition, the design of disclosure controls and procedures must reflect the fact that there are resource constraints and that management is required to apply judgment in evaluating the benefits of possible controls and procedures relative to their costs.

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Based on that evaluation, our Chief Executive Officer and Chief Financial Officer concluded that our disclosure controls and procedures (as defined in Rules 13a-15(e) and 15d-15(e) under the Exchange Act) were effective at the reasonable assurance level as of December 31, 2023.

Management’s Annual Report on Internal Control Over Financial Reporting

Our management is responsible for establishing and maintaining adequate internal control over financial reporting.

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These criteria are in the areas of control environment, risk assessment, control activities, information and communication, and monitoring.

Management’s assessment included extensive documentation, evaluating and testing the design and operating effectiveness of its internal controls over financial reporting.

Based on management’s processes and assessment, as described above, management has concluded that, as of December 31, 2022, our internal control over financial reporting was effective.

Management’s assessment included extensive documentation, evaluating and testing the design and operating effectiveness of its internal controls over financial reporting.

Based on management’s processes and assessment, as described above, management has concluded that, as of December 31, 2023, our internal control over financial reporting was effective.

Attestation Report of the Registered Public Accounting Firm

This Annual Report on Form 10-K does not include an attestation report of our registered public accounting firm due to an exemption established by the JOBS Act for “emerging growth companies.”

Changes in Internal Control over Financial Reporting

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Other Information.

Rule 10b5-1 Trading Plans

During the fiscal quarter ended on December 31, 2023, none of our directors and officers (as defined in Rule 16a-1(f) under the Exchange Act) adopted , modified or terminated a “Rule 10b5-1 trading arrangement” or “non-Rule 10b5-1 trading arrangement,” as those terms are defined in Item 408(a) of Regulation S-K, except as described in the table below:

Name and Title

Duration of Trading Arrangements (1)

Rule 10b5-1 Trading Arrangement?

Aggregate Number of Securities Subject to Trading Arrangement

Steven Nichtberger

Chief Executive Officer

Terminate (2)

November 9, 2023

January 23, 2024 – January 23, 2025

Up to 350,000 shares to be sold

Steven Nichtberger

Chief Executive Officer

November 9, 2023

July 8, 2024 - July 31, 2025

Up to 350,000 shares to be sold

Chief Financial Officer

Terminate (3)

November 9, 2023

October 7, 2023 – October 16, 2024

Up to 50,000 shares to be sold

Chief Financial Officer

November 9, 2023

July 15, 2024 - July 16, 2025

Up to 50,000 shares to be sold

Chief Business Officer

Terminate (4)

November 9, 2023

January 16, 2024 – December 31, 2024

Up to 29,168 shares to be sold

Chief Business Officer

November 9, 2023

July 17, 2024 - July 31, 2025

Up to 29,168 shares to be sold

Gwendolyn Binder

President of Science and Technology

Terminate (5)

November 9, 2023

February 20, 2024 – February 21, 2025

Up to 100,756 shares to be sold

Gwendolyn Binder

President of Science and Technology

November 9, 2023

July 22, 2024 - July 23, 2025

Up to 100,756 shares to be sold

* Denotes whether the trading plan is intended, when adopted, to satisfy the affirmative defense of Rule 10b5-1(c).

(1) Except as indicated by footnote, each trading arrangement permitted or permits transactions through and including the earlier to occur of (a) the completion of all purchases or sales or (b) the date listed in the table.

(2) Represents the modification, as described in Rule 10b5-1(c)(1)(iv) under the Exchange Act, of a written trading arrangement adopted on August 30, 2023 that was intended to satisfy the affirmative defense conditions of Rule 10b5-1(c) under the Exchange Act.

(3) Represents the modification, as described in Rule 10b5-1(c)(1)(iv) under the Exchange Act, of a written trading arrangement adopted on June 8, 2023 that was intended to satisfy the affirmative defense conditions of Rule 10b5-1(c) under the Exchange Act.

(4) Represents the modification, as described in Rule 10b5-1(c)(1)(iv) under the Exchange Act, of a written trading arrangement adopted on September 5, 2023 that was intended to satisfy the affirmative defense conditions of Rule 10b5-1(c) under the Exchange Act.

(5) Represents the modification, as described in Rule 10b5-1(c)(1)(iv) under the Exchange Act, of a written trading arrangement adopted on August 24, 2023 that was intended to satisfy the affirmative defense conditions of Rule 10b5-1(c) under the Exchange Act.

Termination of 2023 At-The-Market Offering

On March 16, 2023, we entered into the 2023 Sales Agreement with the Sales Agent, pursuant to which we could, from time to time, sell shares of our common stock having an aggregate offering price of up to $100.0 million through the Sales Agent, as our agent, or the 2023 ATM Offering.

In connection with the 2023 ATM Offering, we filed a prospectus, dated March 16, 2023, with the 2023 Registration Statement, or the 2023 ATM Prospectus.

Between March 16, 2023 and March 21, 2024, we sold an aggregate of 5,018,969 shares of common stock pursuant to the 2023 Sales Agreement for aggregate gross proceeds of approximately $99.9 million, thereby selling the total amount available under the 2023 Sales Agreement.

Pursuant to the terms of the 2023 Sales Agreement, effective March 21, 2024, or the Termination Date, we terminated the 2023 Sales Agreement, and we have discontinued all offers and sales of shares of our common stock under the 2023 Sales Agreement and the 2023 ATM Prospectus.

All of the continuing obligations under the 2023 Sales Agreement will be terminated as of the Termination Date, other than those provisions which expressly survive termination as provided in the 2023 Sales Agreement.

We are not subject to any termination penalties related to the termination of the 2023 Sales Agreement.

A copy of the 2023 Sales Agreement was filed as Exhibit 1.2 to our Registration Statement on Form S-3 (File No.

333-270599) filed with the SEC on March 16, 2023.

Disclosure Regarding Foreign Jurisdictions that Prevent Inspections.

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Statements of Operations and Comprehensive Loss for the Years Ended December 31, 2023 and 2022

Statements of Stockholders’

Equity for the Years Ended December 31, 2022 and 2021

Statements of Stockholders’ Equity for the Years Ended December 31, 2023 and 2022

Statements of Cash Flows for the Years Ended December 31, 2023 and 2022

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Statements of Operations and Comprehensive Loss for the Years Ended December 31, 2023 and 2022

Statements of Stockholders’

Equity for the Years Ended December 31, 2022 and 2021

Statements of Stockholders’ Equity for the Years Ended December 31, 2023 and 2022

Statements of Cash Flows for the Years Ended December 31, 2023 and 2022

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We have audited the accompanying balance sheets of Cabaletta Bio, Inc.

(the Company) as of December 31, 2022 and 2021, the related statements of operations and comprehensive loss, stockholders’

equity and cash flows for the years then ended, and the related notes (collectively referred to as the “financial statements”).

(the Company) as of December 31, 2023 and 2022, the related statements of operations and comprehensive loss, stockholders’ equity and cash flows for the years then ended, and the related notes (collectively referred to as the “financial statements”).

In our opinion, the financial statements present fairly, in all material respects, the financial position of the Company at December 31, 2023 and 2022, and the results of its operations and its cash flows for the years then ended, in conformity with U.S.

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Basis for Opinion

These financial statements are the responsibility of the Company’s management.

Our responsibility is to express an opinion on the Company’s financial statements based on our audits.

These financial statements are the responsibility of the Company’s management.

Our responsibility is to express an opinion on the Company’s financial statements based on our audits.

We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and are required to be independent with respect to the Company in accordance with the U.S.

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The Company is not required to have, nor were we engaged to perform, an audit of its internal control over financial reporting.

As part of our audits we are required to obtain an understanding of internal control over financial reporting but not for the purpose of expressing an opinion on the effectiveness of the Company’s internal control over financial reporting.

Accordingly, we express no such opinion.

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/s/ Ernst & Young LLP

We have served as the Company’s auditor since 2018

Philadelphia, Pennsylvania

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Total current assets

Property, plant and equipment, net

Property and equipment, net

Operating lease right-of-use assets

Liabilities and stockholders’

Liabilities and stockholders’ equity

Current liabilities:

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Total Liabilities

Commitments and contingencies (see Note 7)

Stockholders’

Commitments and contingencies (see Notes 6 and 7)

Stockholders’ equity:

Preferred stock, $ 0.00001 par value:

10,000,000 shares authorized and no

shares issued or outstanding as of December 31, 2022 and 2021

10,000,000 shares authorized as of December 31, 2023 and 2022;

no shares issued or outstanding at December 31, 2023 or 2022

Voting and non-voting common stock, $ 0.00001 par value:

( 143,590,481 voting and 6,409,519 non-voting) shares authorized as of

December 31, 2022 and 2021;

29,445,134 ( 27,584,375 voting and

1,860,759 non-voting) shares issued and outstanding as of

December 31, 2022 and 28,927,129 ( 24,614,629 voting and

4,312,500 non-voting) shares issued and outstanding as

of December 31, 2021

150,000,000 ( 143,590,481 voting and 6,409,519 non-voting) shares authorized as of December 31, 2023 and December 31, 2022;

47,823,232 ( 46,378,937 voting and 1,444,295 non-voting) shares issued and outstanding as of December 31, 2023 and 29,445,134 ( 27,584,375 voting and 1,860,759 non-voting) shares issued and outstanding as of December 31, 2022

Additional paid-in capital

Accumulated other comprehensive income

Accumulated other comprehensive income (loss)

Accumulated deficit

Total stockholders’

Total liabilities and stockholders’

Total stockholders’ equity

Total liabilities and stockholders’ equity

The accompanying notes are an integral part of these financial statements.

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(in thousands, except share and per share amounts)

Year Ended December 31,

Operating expenses:

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Interest income

Other comprehensive loss:

Net unrealized loss on available-for-sale investments, net of tax

Other comprehensive income (loss):

Net unrealized income (loss) on available-for-sale investments, net of tax

Net comprehensive loss

Net loss per voting and non-voting share, basic and diluted

Net loss per share of voting and non-voting common stock, basic and diluted

The accompanying notes are an integral part of these financial statements.

CABALETTA BIO, INC.

Statements of Stockholders’

Statements of Stockholders’ Equity

(in thousands, except share and per share amounts)

Additional Paid-in Capital

Accumulated Other Comprehensive Loss

Paid-in Capital

Accumulated Other Comprehensive Income (Loss)

Accumulated Deficit

Total Stockholders’

Balance—December 31, 2020

Common stock issuance, net of issuance costs of

Issuance of common stock in connection with

exercise of stock options

Issuance of common stock under employee stock

purchase plan

Stockholders’ Equity

Balance—December 31, 2021

Issuance of common stock and pre-funded warrants for the purchase of common stock, net of issuance costs of $ 2,438

Issuance of common stock upon exercise of pre-funded warrants

Issuance of common stock in connection with exercise of stock options

Issuance of common stock under employee stock purchase plan

Net unrealized losses on available-for-sale securities

Stock-based compensation

Balance—December 31, 2021

Issuance of common stock and pre-funded warrants

for the purchase of common stock, net of issuance

costs of $ 2,438

Issuance of common stock upon exercise of

pre-funded warrants

Issuance of common stock in connection with

exercise of stock options

Issuance of common stock under employee stock

purchase plan

Net unrealized losses on available-for-sale securities

Balance—December 31, 2022

Stock-based compensation

Balance—December 31, 2022

Issuance of common stock, net of issuance costs of $ 8,647

Issuance of common stock in connection with exercise of stock options

Issuance of common stock under employee stock purchase plan

Issuance of common stock upon exercise of pre-funded warrants

Net unrealized gains on available-for-sale securities

Balance—December 31, 2023

The accompanying notes are an integral part of these financial statements.

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Gain on derecognition of embedded lease upon lease amendment

Amortization of (discount) premium on investments

Amortization of discount on investments

Changes in operating assets and liabilities:

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Proceeds from maturities of investments

Net cash (used in) provided by investing activities

Net cash used in investing activities

Cash flows from financing activities:

Proceeds from issuance of common stock and pre-funded warrants,

net of issuance costs

Proceeds from issuance of common stock in connection with

the exercise of stock options

Proceeds from the issuance of common stock under employee

stock purchase plan

Proceeds from the issuance of common stock, net of issuance costs

Proceeds from issuance of common stock in connection with the exercise of stock options

Proceeds from issuance of common stock under employee stock purchase plan

Net cash provided by financing activities

Net (decrease) increase in cash and cash equivalents

Cash and cash equivalents—beginning of year

Cash and cash equivalents—end of year

Supplemental disclosures of non-cash investing and

financing activities:

Net increase (decrease) in cash and cash equivalents

Cash and cash equivalents—beginning of period

Cash and cash equivalents—end of period

Supplemental disclosures of non-cash investing and financing activities:

Property and equipment purchases included in accounts payable

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If the Company fails to become profitable or is unable to sustain profitability on a continuing basis, then it may be unable to continue its operations at planned levels and be forced to reduce its operations.

In December 2019, a novel strain of coronavirus (COVID-19) surfaced in Wuhan, China and proceeded to spread globally.

Although many activities have returned to normal, new variants of COVID-19 have been identified and spread, which have led to various responses, including government-imposed quarantines, travel restrictions and other public health safety measures.

The extent to which COVID-19 will continue to impact the Company’s operations or those of its third party partners will depend on future developments, which are uncertain and cannot be predicted with confidence, including new information that may emerge concerning the severity of COVID-19, the impact of new strains of the virus, the effectiveness, availability and utilization of vaccines and treatments and the actions to contain COVID-19 or treat its impact, among others.

The Company’s financial results to date have not been significantly impacted by COVID-19, however, the Company cannot at this time predict the specific extent, duration, or full impact that the ongoing COVID-19 pandemic will have on its financial condition, operations, and business plans, including its ability to raise additional capital, the timing and enrollment of patients in its ongoing and planned clinical trials, future financings and other expected milestones of its product candidates.

The Company has sustained annual operating losses since inception and expects to continue to generate operating losses for the foreseeable future.

The Company’s ultimate success depends on the outcome of its research and development activities.

The Company had cash and cash equivalents and investments of $ 241,249 as of December 31, 2023.

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However, if such financing is not available at adequate levels and on a timely basis, or such agreements are not available on favorable terms, or at all, as and when needed, the Company will need to reevaluate its operating plan and may be required to delay or discontinue the development of one or more of its product candidates or operational initiatives.

The Company expects that its cash and cash equivalents and investments as of December 31, 2022 will be sufficient to fund its projected operations for

at least 12 months following the date the Company files this Annual Report on Form 10-K with the Securities and Exchange Commission (SEC).

The Company expects that its cash and cash equivalents and investments as of December 31, 2023 will be sufficient to fund its projected operations for at least 12 months following the date the Company files this Annual Report on Form 10-K with the Securities and Exchange Commission (SEC).

Summary of Significant Accounting Policies

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The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of expenses during the reporting period.

Significant estimates and assumptions made in the accompanying financial statements include but are not limited to the valuation allowance on the Company’s deferred tax assets and certain accruals.

Significant estimates and assumptions made in the accompanying financial statements include but are not limited to advance payments and accruals related to the Company’s research and development expenses .

The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate.

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Off-Balance Sheet Risk and Concentrations of Credit Risk

Financial instruments, which potentially subject the Company to significant concentrations of credit risk, consist primarily of cash and cash equivalents, which are primarily invested in U.S.

Financial instruments, which potentially subject the Company to significant concentrations of credit risk, consist of cash and cash equivalents, which are invested in U.S.

treasury-based money market funds, and available-for-sale debt securities, which are invested in U.S.

government securities.

A portion of the Company’s cash is maintained at a federally insured financial institution.

The deposits held at this institution are in excess of federally insured limits.

treasury securities.

A portion of the Company’s cash is maintained at two federally insured financial institutions, and account balances may at times exceed federally insured limits.

The Company has not experienced any losses in such accounts and management believes that the Company is not exposed to significant credit risk.

The cash in this account is swept daily into U.S.

treasury-based and U.S.

government-based money market funds.

The Company has no off‑balance sheet risk, such as foreign exchange contracts, option contracts, or other foreign hedging arrangements.

Cash and Cash Equivalents

The Company has no off‑balance sheet risk, such as foreign exchange contracts, option contracts, or other foreign hedging arrangements.

The Company considers all highly liquid investments purchased with original maturities of three months or less from the purchase date to be cash equivalents.

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Investments are available-for-sale and carried at estimated fair value.

The Company’s valuations of available-for-sale debt securities are generally derived from independent pricing services based upon quoted prices in active markets for similar securities, with prices adjusted for yield and number of days to maturity, or based on industry models using data inputs, such as interest rates and prices that can be directly observed or corroborated in active markets.

Management determines the appropriate classification of its investments in debt securities at the time of purchase and at the end of each reporting period.

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The Company periodically evaluates whether declines in fair values of its available-for-sale securities below their book value are other-than-temporary.

This evaluation consists of several qualitative and quantitative factors including the severity and duration of the unrealized loss as well as the Company’s ability and intent to hold the available-for-sale security until a forecasted recovery occurs.

Additionally, the Company assesses whether it has plans to sell the security or if more likely than not it will be required to sell any available-for-sale securities before recovery of its amortized cost basis.

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The authoritative guidance on fair value measurements establishes a three-tier fair value hierarchy for disclosure of fair value measurements as follows:

Level 1—Observable inputs such as unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date.

Level 2—Inputs (other than quoted prices included in Level 1) that are either directly or indirectly observable for the asset or liability.

Level 1—Observable inputs such as unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date.

Level 2—Inputs (other than quoted prices included in Level 1) that are either directly or indirectly observable for the asset or liability.

These include quoted prices for similar assets or liabilities in active markets and quoted prices for identical or similar assets or liabilities in markets that are not active.

Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

The Company has leases related to its facilities used for office and laboratory space, which are classified as operating leases.

These leases result in operating right-of-use (ROU) assets, current operating lease liabilities, and non-current operating lease liabilities in the balance sheets and have remaining lease terms up to 2.5 years.

Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

The Company has leases related to its facilities used for offices, laboratory space and manufacturing, which are classified as operating leases.

These leases result in operating right-of-use (ROU) assets, current operating lease liabilities, and non-current operating lease liabilities in the accompanying balance sheets.

The Company does not have any financing leases.

Leases with a term of 12 months or less are considered short-term and a ROU asset and lease obligation are not recognized.

Leases with terms of 12 months or less are considered short-term leases and ROU assets and lease obligations are not recognized.

Payments associated with short-term leases are expensed on a straight-line basis over the lease term.

ROU assets represent the right to use an underlying asset for the lease term and the lease liabilities represent an obligation to make lease payments arising from the lease, measured at the present value of the lease payments not yet paid discounted using the discount rate for the lease established at the lease commencement date.

ROU assets represent the right to use an underlying asset for the lease term and the lease liabilities represent an obligation to make lease payments arising from the lease.

Lease liabilities are measured at the present value of the lease payments not yet paid discounted using the discount rate for the lease established at the lease commencement date.

Operating lease ROU assets and liabilities are recognized at the lease commencement date based on the present value of lease payments over the life of the lease term.

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The operating lease ROU assets also include any prepaid lease payments made and any other indirect costs and excludes any lease incentives received.

Lease terms may include the impact of options to extend or terminate the lease when it is reasonably certain that the Company will exercise that

Lease terms may include the impact of options to extend or terminate the lease when it is reasonably certain that the

Company will exercise those options.

Lease cost for operating leases is recognized on a straight-line basis over the lease term.

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Research and development costs include costs incurred for internal and external research and development activities and are expensed as incurred in the accompanying statements of operations.

Research and development costs consist of salaries and benefits, including associated stock-based compensation, and laboratory supplies and facility costs, as well as fees paid to entities that conduct certain research and development and clinical trial activities on the Company’s behalf.

The Company records accrued liabilities for estimated costs of research and development activities conducted by service providers, which include activities under agreements with Penn (Note 6), the conduct of sponsored research, preclinical studies, contract manufacturing activities and clinical trial activities.

The Company records the estimated costs of research and development activities based upon the estimated amount of services provided and includes these costs in accrued and other current liabilities and prepaid expenses and other current assets in the accompanying balance sheets and within research and development expense in the accompanying statements of operations.

The Company records accrued liabilities for estimated costs of research and development activities conducted by service providers, which include preclinical studies, contract manufacturing activities and clinical trial activities.

The Company records the estimated costs of research and development activities based upon the estimated amount of services provided and includes these costs in accrued and other current liabilities in the accompanying balance sheets and within research and development expense in the accompanying statements of operations.

Non-refundable advance payments made for goods or services that will be used or rendered for future research and development activities are deferred and capitalized and recognized as expense as the goods are received or the related services are rendered.

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The Company uses the asset and liability method of accounting for income taxes.

Deferred tax assets and liabilities, which relate primarily to the carrying amount of the Company’s property and equipment and its net operating loss carryforwards, are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled.

Deferred tax expense or benefit is the result of changes in the deferred tax assets and liabilities.

Deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to temporary differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax base, as well as for net operating loss carryforwards and research and development credits, and are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled.

Valuation allowances are established when necessary to reduce deferred tax assets where, based upon the available evidence, the Company concludes that it is more-likely-than-not that the deferred tax assets will not be realized.

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Net Loss Per Share

The Company calculates basic and diluted net loss per share attributable to common stockholders in conformity with the two-class method required for participating securities.

The Company calculates basic and diluted net loss per share in conformity with the two-class method required for participating securities.

The Company has voting and non-voting common stock.

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Each share of non-voting common stock may be converted at any time into one share of voting common stock at the option of its holder by providing written notice to the Company, subject to the limitations provided for in the amended and restated certificate of incorporation.

Basic net loss per share attributable to common stockholders is computed by dividing the net loss attributable to common stockholders by the weighted average number of shares of common stock, including pre-funded warrants to purchase shares of common stock that were issued in a financing transaction in December 2022.

Basic net loss per share attributable to common stockholders is computed by dividing the net loss by the weighted average number of shares of common stock, including pre-funded warrants to purchase shares of common stock that were issued in a financing transaction in December 2022.

The undistributed loss for each year is allocated to common stockholders based on the contractual participation rights of the voting and non-voting common stock as if the losses for the year had been distributed.

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Operating segments are defined as components of an entity for which separate financial information is available and that is regularly reviewed by the Chief Operating Decision Maker (CODM) in deciding how to allocate resources to an individual segment and in assessing performance.

The Company’s CODM is its Chief Executive Officer.

The Company has determined it operates in a single operating segment and has one reportable segment.

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The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs until such financings are consummated.

After consummation of the equity financing, these costs are recorded as a reduction to the carrying value of stockholders’

equity as a reduction of additional paid-in capital or equity generated as a result of such offering.

Should an in-process equity financing be abandoned, the deferred offering costs will be expensed immediately as a charge to operating expenses in the consolidated statements of operations and comprehensive loss.

After consummation of the equity financing, these costs are recorded as a reduction to the carrying value of stockholders’ equity as a reduction of additional paid-in capital or equity generated as a result of such offering.

Should an in-process equity financing be abandoned, the deferred offering costs will be expensed immediately as a charge to operating expenses in the statements of operations and comprehensive loss.

Emerging Growth Company Status

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As a result, these financial statements may not be comparable to companies that comply with the new or revised accounting pronouncements as of public company effective dates.

Recently Adopted Accounting Pronouncements

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) , which requires lessees to recognize right of use assets and corresponding lease liabilities on the balance sheet for all leases (with the exception of short-term leases).

This update also requires lessees and lessors to disclose key information about their leasing transactions.

Topic 842 is effective for public companies for annual and interim periods beginning after December 15, 2018.

In June 2020, the FASB granted a one-year effective date delay for certain companies applying leases guidance to fiscal years beginning after December 15, 2021, and interim periods within fiscal years beginning after December 15, 2022.

As permitted for emerging growth companies, the Company adopted Topic 842 under the private company transition guidance for the annual period ended December 31, 2022.

The Company adopted the standard effective January 1, 2022 using the modified retrospective approach to not restate comparative periods and recognized operating lease right-of-use assets and operating lease liabilities of $8,282 and $8,297, respectively.

The adoption of Topic 842 did not result in a material impact to the Company’s statement of operations and comprehensive loss for the year ended December 31, 2022.

There was no impact to the financial statements for the prior periods presented due to the transition method elected.

The Company elected the package of practical expedients permitted under the transition guidance, which, among other things, allowed the Company to carry forward the historical lease classification.

Additionally, the Company elected the practical expedient to not separate non-lease components from the lease components to which they relate, and instead account for each separate lease and non-lease component associated with that lease component as a single lease component for all underlying asset classes.

Recently Issued Accounting Pronouncements

In November 2023, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, 2023-07, Segment Reporting (Topic 280) – Improvements to Reportable Segment Disclosures .

This ASU requires that a public entity provide additional segment disclosures on an interim and annual basis.

The amendments in this ASU should be applied retrospectively to all prior periods presented in the financial statements, unless impracticable.

Upon transition, the segment expense categories and amounts disclosed in the prior periods should be based on the significant segment expense categories identified and disclosed in the period of adoption.

The ASU is effective for fiscal years beginning after December 15, 2023 and interim periods within fiscal years beginning after December 15, 2024.

Early adoption is permitted.

The Company is currently planning to adopt this guidance when effective and is assessing the impact of the adoption on the Company’s financial statements and accompanying footnotes.

In December 2023, the FASB issued ASU 2023-09, Improvements to Income Tax Disclosures .

ASU 2023-09 enhances the transparency about income tax information through improvements to income tax disclosures primarily related to the rate reconciliation and income taxes paid information.

The guidance is effective for public business entities for annual periods beginning after December 15, 2024.

Early adoption is permitted.

The Company is currently planning to adopt this guidance when effective and is assessing the impact of the adoption on the Company’s financial statements and accompanying footnotes.

Fair Value Measurements

As of December 31, 2022 and 2021, the Company’s financial instruments included cash and cash equivalents, available-for-sale debt securities, accounts payable and accrued expenses.

The carrying amounts for cash and cash equivalents, accounts payable and accrued expenses reported in the Company’s financial statements for these instruments approximate their respective fair values because of the short-term nature of these instruments.

The following tables present information about the Company’s financial assets measured at fair value on a recurring basis and indicate the level of the fair value hierarchy utilized to determine such fair values:

As of December 31, 2023 and 2022, the Company’s financial instruments included cash and cash equivalents, available-for-sale debt securities, accounts payable and accrued expenses.

December 31, 2023

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Financial assets

Cash and cash equivalents:

Cash equivalents:

Money market funds

Treasury securities - original maturity less than three months

Short-term investments:

Government securities

Treasury securities

December 31, 2022

Quoted Prices in Active Markets for Identical Assets (Level 1)

Significant Other Observable Inputs (Level 2)

Significant Unobservable Inputs (Level 3)

Active Markets

for Identical

Assets (Level 1)

Financial assets

Cash and cash equivalents:

Cash equivalents:

Money market funds

Short-term investments:

Treasury securities

Money market funds are measured at fair value on a recurring basis using quoted prices and are classified as Level 1.

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For debt securities classified as available-for-sale investments, the Company records unrealized gains or losses resulting from changes in fair value between measurement dates as a component of other comprehensive income:

The Company did no t hold any available-for-sale securities as of December 31, 2021.

December 31, 2023

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Money market funds

Treasury securities - original maturity less than three months

Included in cash and cash equivalents

Government securities - due in one year or less

Treasury securities - due in one year or less

Included in short-term investments

December 31, 2022

Amortized Cost

Gross Unrealized Gains

Gross Unrealized Losses

Financial assets

Money market funds

Included in cash and cash equivalents

Treasury securities - due in one year or less

Included in short-term investments

Property, Plant and Equipment

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Collaborations, Licensing Agreements and other Agreements

Amended and Restated License Agreement with the Trustees of the University of Pennsylvania and Children’s Hospital of Philadelphia

In August 2018, the Company entered into a license agreement with Penn, as amended and restated in July 2019 to include the Children’s Hospital of Philadelphia (CHOP) as a party, and as amended in May 2020 and October 2021 (the License Agreement) pursuant to which the Company obtained (a) a non-exclusive, non-sublicensable worldwide license to certain of Penn’s intellectual property to conduct research, product development, clinical trials, cell manufacturing and other activities, and (b) an exclusive, worldwide, royalty-bearing right and license, with a right to sublicense, on a target-by-target basis, under certain of Penn’s intellectual property to make, use, sell, offer for sale, import, and otherwise commercialize products for the treatment of autoimmune and alloimmune diseases.

Unless earlier terminated, the License Agreement expires on the expiration or abandonment or other termination of the last valid claim in Penn’s intellectual property licensed by the Company.

Amended and Restated License Agreement with the Trustees of the University of Pennsylvania and Children’s Hospital of Philadelphia

Unless earlier terminated, the License Agreement expires on the expiration or abandonment or other termination of the last valid claim in Penn’s intellectual property licensed by the Company.

The Company may terminate the License Agreement at any time for convenience upon 60 days written notice.

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Under the terms of the License Agreement, the Company was obligated to pay $ 2,000 annually for three years beginning August 2018 for funding to the laboratories of each of Drs.

Milone and Payne (see Sponsored Research Agreements ).

Milone and Payne.

This was satisfied through completed sponsored research agreements with a total cost of $ 12,560 .

During the term of the License Agreement until the first commercial sale of the first product, the Company is obligated to pay Penn a non-refundable, non-creditable annual license maintenance fee of $ 10 .

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To the extent the Company sublicenses its license rights under the License Agreement, Penn would be eligible to receive tiered sublicense income at percentage rates in the mid-single to low double-digits.

There were no amounts due under the License Agreement as of December 31, 2022 or 2021.

Sponsored Research Agreements

The Company has sponsored research agreements with two faculty members at Penn, who are also scientific co-founders of the Company and members of the Company’s scientific advisory board.

In May 2020, one of the agreements was amended to expand the scope of sponsored research.

In August 2020, this agreement was further amended to extend the term of the original research plan.

In December 2021, the Company further amended this SRA to extend the term through December 2024 and expand the workplan to include additional correlative studies related to the DesCAARTes TM trial.

In December 2022, the Company signed a budget amendment to this SRA.

In April 2021 and October 2021, the other SRA was amended to extend the term of the original research plan.

Under the amended SRAs, the Company had committed to funding defined research plans through December 2024, or through completion of research activities, and November 2022 , respectively.

The total estimated cost of $ 12,560 under the SRAs satisfies the Company’s annual obligation under the License Agreement (see Amended and Restated License Agreement with the Trustees of the University of Pennsylvania above).

As of December 31, 2022, the full cost of these SRAs has been incurred pursuant to the agreements.

For the years ended December 31, 2022 and 2021, the Company recognized research and development expense of $ 2,624 and $ 2,840 , respectively, related to these SRAs in the accompanying statements of operations.

As of December 31, 2022 and 2021, there was $ 77 and $ 36 included in Accrued and other current liabilities in the accompanying balance sheets as of December 31, 2022 and 2021.

There were no amounts due under the License Agreement as of December 31, 2023.

Master Translational Research Services Agreement

In October 2018, the Company entered into a services agreement (the Services Agreement) with Penn for additional research and development services from various laboratories within Penn.

The research and development activities are detailed in separately executed Penn organization-specific addenda.

In October 2018 and February 2023, the Company entered into services agreements (the CAART and CARTA Services Agreements) with Penn for research, development and manufacturing services from various laboratories within Penn.

The activities are detailed in separately executed Penn organization-specific addenda.

In May 2020, the Company amended its Addendum with the Center for Advanced Retinal and Ocular Therapeutics (CAROT) to expand access to vector manufacturing.

Research and development expense related to executed addenda under the master translational research service agreement with Penn recognized in the accompanying statements of operations for the years ended December 31, 2022 and 2021 was $ 2,623 and $ 1,933 , respectively.

Research and development expense related to executed addenda under the master translational research service agreements with Penn recognized in the accompanying statements of operations for the years ended December 31, 2023 and 2022 was $ 3,786 and $ 2,623 , respectively.

The Company is committed to pay up to $ 3,000 under the CARTA Services Agreement for cell processing manufacturing through December 31, 2024.

The Company may incur additional expenses of approximately $ 643 through the remaining term of the CAROT Amended Addendum.

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IASO is also eligible to receive up to mid double digit millions in milestone payments based upon the achievement of specified pre-clinical, development and regulatory milestones, and up to an additional low triple digit millions in milestone payments based upon achievement of specified sales milestones, for a total consideration, inclusive of the upfront payment, of up to $ 162,000 , along with tiered mid-single digit royalties on future net sales for licensed products that may result from the IASO Agreement.

Upon the U.S.

Food and Drug Association’s clearance of the CABA-201 Investigational New Drug application for the treatment of systemic lupus erythematosus in March 2023, a milestone payment of $ 1,000 was recognized in the accompanying statements of operations.

No amount was owed to IASO as of December 31, 2023.

A milestone payment of $ 1,500 was paid to IASO in the first quarter of 2024 after the first patient in a CABA-201 trial was dosed.

IASO has the right of first negotiation if the Company desires to grant a third party an exclusive license to develop, manufacture, commercialize or otherwise exploit the licensed products in the Greater China region.

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In July 2020 and as amended in January 2023, the Company entered into a collaboration and license agreement with Artisan Bio, Inc.

(Artisan), wherein the Company and Artisan agreed to collaborate to potentially enhance certain pipeline products of the Company at specific targets using Artisan’s gene editing and engineering technology.

If the Artisan technology is applied to any of the Company’s products, the Company will be responsible for the development, manufacturing, and commercialization of any such products.

Under the terms of the agreement, the Company was required to pay Artisan a nominal upfront fee, as well as costs associated with research and development activities.

Artisan is eligible to receive future research, development and regulatory milestones, and is also eligible to receive sales milestones and tiered royalties on net sales of products that incorporate the Artisan technology.

The Company can terminate the agreement at will upon advance written notice with payment of a nominal cancellation fee.

Artisan is eligible to receive future development and regulatory milestones, and is also eligible to receive sales milestones and tiered royalties on net sales of products that incorporate the Artisan technology.

The Company can terminate the agreement at will upon advance written notice at no cost.

In January 2024, the Company was notified that the agreement would be assigned in connection with Artisan's general assignment for the benefit of creditors.

The agreement remains effective.

Licence and Supply Agreement with Oxford Biomedica

In December 2021, the Company entered into a Licence and Supply agreement (LSA) with Oxford Biomedica (UK) Limited, wherein the LSA grants the Company a non-exclusive license to Oxford’s LentiVector® platform for its application in the Company’s DSG3-CAART program and puts in place a multi-year vector supply agreement.

Under the terms of the agreement, the Company is required to pay Oxford an upfront fee, as well as costs associated with initial vector manufacturing activities for a total cost of up to approximately $ 4,000 .

As of December 31, 2022, a total project to date expense of $ 1,100 has been recognized.

In December 2021, the Company entered into a Licence and Supply agreement (LSA) with Oxford Biomedica (UK) Limited (Oxford), wherein the LSA grants the Company a non-exclusive license to Oxford’s LentiVector® platform for its application in the Company’s DSG3-CAART program and puts in place a multi-year vector supply agreement.

Under the terms of the agreement, the Company was required to pay Oxford an upfront fee, as well as costs associated with initial vector manufacturing activities for a total cost of up to approximately $ 4,000 , of which project to date expense of $ 1,100 has been recognized.

Oxford is eligible to receive regulatory and sales milestones in the low tens of millions and royalties in the low single digits on net sales of products that incorporate the Oxford technology.

The Company can terminate the agreement at will upon advance written notice and subject to certain manufacturing slot cancellation fees.

In May 2023, the Company amended the LSA with Oxford to expand the license to include the Company's CABA-201 program for an upfront fee of $ 500 and in August 2023, the Company and Oxford entered into a vector supply agreement for CABA-201, and a related second amendment to the LSA, with a total cost under the vector supply agreement of up to approximately $ 5,000 , of which approximately $ 1,520 was recognized as expense in the accompanying statements of operations for the year ended December 31, 2023.

In February 2024, the Company and Oxford entered into a third amendment of the LSA to update the patent schedule.

Option and License Agreement with Autolus

In January 2023, the Company entered into an Option and License Agreement (Autolus Agreement) with Autolus Holdings (UK) Limited (Autolus), wherein the Autolus Agreement granted the Company a non-exclusive license to access Autolus' RQR8 technology in its CD19-CAR T cell therapy program, and subject to additional nominal option exercise fees, up to four additional targets.

Under the terms of the Autolus Agreement, the Company was required to pay Autolus an upfront license fee of $ 1,200 , recognized as expense in the first quarter of 2023 in the accompanying statements of operations, of which $ 1,100 was paid in 2023 and $ 100 was paid in January 2024.

Autolus is also eligible to receive regulatory milestones of up to $ 12,000 for each licensed target, sales milestones of up to a total of $ 15,000 and royalties in the low single digits on net sales of all products that incorporate the RQR8 technology.

The Autolus Agreement will continue on a country-by-country, licensed product-by-licensed product basis until the expiration of the royalty term as identified in the Autolus Agreement, unless earlier terminated.

The Company can terminate the Autolus Agreement at will upon advance written notice.

Each of the Company and Autolus may terminate the Agreement for a material, uncured breach or insolvency of the other party.

Commitments and Contingencies

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In January 2021, the Company entered into a Development and Manufacturing Services Agreement (WuXi Agreement) with WuXi Advanced Therapies, Inc.

(WuXi) to serve as the Company’s cell processing manufacturing partner for the MuSK-CAART Phase 1 clinical trial, or MusCAARTes TM trial.

The WuXi Agreement will expire the later of January 2024 , or upon completion of WuXi’s services related to the MusCAARTes TM trial.

The Company has the right to terminate the WuXi Agreement for convenience or other reasons specified in the WuXi Agreement upon prior written notice.

If the Company terminates the WuXi Agreement, it will be obligated to pay an early termination fee of up to $ 1,500 .

Leases for disclosure on an embedded lease in the WuXi Agreement that was derecognized in August 2022.

Research Service Agreement

In February 2021, the Company entered into a research service agreement with CHOP for vector manufacturing.

In May 2021, this agreement was amended to provide additional vector manufacturing services.

Research and development expense related to this research service agreement with CHOP recognized in the accompanying statements of operations was $ 166 and $ 1,071 for the years ended December 31, 2022 and 2021, respectively.

The Company may incur additional costs of approximately $ 480 under this agreement.

(WuXi) to serve as an additional cell processing manufacturing partner for the MuSK-CAART Phase 1 clinical trial, or MusCAARTes TM trial.

The WuXi Agreement is scheduled to expire upon completion of WuXi’s services related to MuSK-CAART and CABA-201.

In August 2023, the Company

entered into new work orders under the WuXi Agreement for WuXi to serve as one of the Company’s cell processing manufacturing partners for the planned global clinical development of CABA-201 in multiple indications, including potential late-stage clinical trials and commercial readiness activities for CABA-201.

Under the August 2023 work orders, WuXi converted the Company’s non-dedicated suite to a dedicated suite for GMP manufacturing for the Company’s CABA-201 and MuSK-CAART programs, or the Dedicated Suite, for an initial term of 18 months with two 18-month extensions at the Company’s sole option on six months' notice prior to the end of the term.

In addition, the Company agreed to certain monthly minimum runs.

In lieu of the original $ 1,500 termination fee under the terms of the WuXi Agreement, the Company would incur a $ 1,080 termination fee if it terminates both the CABA-201 and MuSK-CAART work orders for any reason.

The Company may terminate for convenience the WuXi Agreement or any work order with six months' prior written notice, however, the Company may not terminate the Dedicated Suite without terminating both the MuSK-CAART and CABA-201 GMP run work orders.

WuXi may terminate for convenience the WuXi Agreement or any work order on 18 months' prior written notice, but such notice may not be effective prior to February 2028.

Other Purchase Commitments

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The Company enters into certain types of contracts that contingently requires the Company to indemnify various parties against claims from third parties.

These contracts primarily relate to (i) the Company’s bylaws, under which the Company must indemnify directors and executive officers, and may indemnify other officers and employees, for liabilities arising out of their relationship, (ii) contracts under which the Company must indemnify directors and certain officers and consultants for liabilities arising out of their relationship, (iii) contracts under which the Company may be required to indemnify partners against certain claims, including claims from third parties asserting, among other things, infringement of their intellectual property rights, and (iv) procurement, consulting, or license agreements under which the Company may be required to indemnify vendors, consultants or licensors for certain claims, including claims that may be brought against them arising from the Company’s acts or omissions with respect to the supplied products, technology or services.

From time to time, the Company may receive indemnification claims under these contracts in the normal course of business.

In addition, under these contracts, the Company may have to modify the accused infringing intellectual property and/or refund amounts received.

In the event that one or more of these matters were to result in a claim against the Company, an adverse outcome, including a judgment or settlement, may cause a material adverse effect on the Company’s future business, operating results or financial condition.

It is not possible to determine the maximum potential amount under these contracts due to the limited history of prior indemnification claims and the unique facts and circumstances involved in each particular agreement.

On February 28, 2022, a purported stockholder of the Company filed a complaint against the Company and certain of the Company’s current officers and certain of the Company’s current and former directors in the United States District Court for the Eastern District of Pennsylvania captioned Patterson v.

Cabaletta Bio, Inc., et al..

2:22-cv-00737 (E.D.

The complaint was filed on behalf of a putative class of persons and entities who purchased or otherwise acquired (a) Cabaletta common stock pursuant and/or traceable to the offering documents issued in connection with the Company’s October 24, 2019 initial public offering;

and/or (b) Cabaletta securities between October 24, 2019 and December 13, 2021 both dates inclusive.

The complaint alleged claims under Sections 10(b) and 20(a) of the Exchange Act and Rule 10b-5 promulgated thereunder and under Sections 11 and 15 of the Securities Act based upon allegedly false or misleading statements and omissions regarding our DesCAARTes TM Phase 1 clinical trial of DSG3-CAART, clinical data for the DesCAARTes TM trial, the efficacy of DSG3-CAART, and the clinical and/or commercial prospects for DSG3-CAART.

The complaint sought damages, prejudgment and post-judgment interest, and reasonable attorneys’

fees, expert fees and other costs.

On October 17, 2022, this complaint was voluntarily dismissed by the plaintiff.

The Company may become subject to additional securities class action lawsuits in the future.

From time to time, the Company may become involved in litigation or legal proceedings.

While the outcome of any such proceedings cannot be predicted with certainty, as of December 31, 2023, the Company is not involved in any material litigation or legal proceedings that it would expect to have a material adverse impact on its financial position, results of operations, or cash flows.

The Company determines whether an arrangement is or contains a lease based on the unique facts and circumstances present at the inception of an arrangement.

The Company leases office and laboratory space under operating leases that have a weighted average remaining term of 2.5 years as of December 31, 2022.

The Company also leases office space under short-term leases that provide for either party to terminate the lease without cause and with 30 days’

The Company’s operating leases include rent escalations and are subject to additional variable charges, including common area maintenance, property taxes and property insurance.

The Company leases office and laboratory space and a

dedicated manufacturing suite at WuXi under operating leases that have a weighted average remaining term of 1.5 years and 2.5 years as of December 31, 2023 and 2022, respectively.

As described further in Note 7, in August 2023, the Company entered into new work orders under the WuXi Agreement for WuXi to serve as one of the Company’s cell processing manufacturing partners for the global clinical development of CABA-201.

WuXi converted the Company’s non-dedicated suite to a Dedicated Suite for GMP manufacturing for the Company’s CABA-201 and MuSK-CAART programs, for an initial term of 18 months.

The terms of the August 2023 work orders included both fixed costs and contingent variable costs.

The lease commenced October 1, 2023, and a right of use asset and lease liability of $ 953 was initially recorded for the fixed payments.

Subsequent to December 31, 2023, the contingency related to the variable costs was resolved which resulted in an additional $ 4,350 in fixed undiscounted lease payments which will be made through the end of the lease.

The Company may terminate for convenience with six months’ prior written notice and a $ 1,080 termination fee, the Dedicated Suite lease if both the CABA-201 and MuSK-CAART work orders are terminated.

The Company also leases office space under short-term leases that provide for either party to terminate the lease without cause and with 30 days’ notice.

The Company’s operating leases include rent escalations and are subject to additional variable charges, including common area maintenance, property taxes and property insurance.

Given the variable nature of such costs, they are recognized as expense as incurred.

Additionally, some of the Company’s leases are subject to certain fixed fees which the Company has determined to be non-lease components.

The Company has elected the practical expedient to account for lease and non-lease components as a single-lease component and has included fixed payments related to non-lease components in calculating the operating lease liability.

In January 2021, the Company entered into the WuXi Agreement.

The Company concluded the WuXi Agreement had an embedded lease as a dedicated manufacturing suite was to be used for the Company’s cell processing manufacturing.

The Company classified the embedded lease as an operating lease and recognized a right-of-use asset and lease liability of $ 7,563 as of January 1, 2022.

In August 2022, the Company's dedicated suite arrangement was converted into a shared suite arrangement.

The Company concluded the WuXi Agreement no longer contained an embedded lease and recognized a gain on derecognition of this lease asset and liability of $ 149 for the year ended December 31, 2022.

The weighted average discount rate for the Company’s operating leases as of December 31, 2022 is 8.3 %, representing the Company's incremental borrowing rate.

For the year ended December 31, 2022, total lease cost was $ 3,849 , consisting of $ 3,042 operating lease cost, $ 36 of variable lease costs and $771 of short-term lease cost.

Cash paid for amounts included in the measurement of operating lease liabilities was $ 2,910 for the year ended December 31, 2022.

Rent expense for the year ended December 31, 2021 was $ 752 .

The weighted average discount rate for the Company’s operating leases is 9.5 % and 8.3 % as of December 31, 2023 and 2022, respectively, representing the Company's incremental borrowing rate at the beginning of each lease.

For the year ended December 31, 2023, total lease cost was $ 3,259 , consisting of $ 2,477 operating lease costs, $ 65 of variable lease costs and $ 717 of short-term lease cost.

Cash paid for amounts included in the measurement of operating lease liabilities was $ 2,456 and $ 2,910 for the years ended December 31, 2023 and 2022, respectively.

For the year ended December 31, 2022, total lease cost was $ 3,849 , consisting of $ 3,042 operating lease costs, $ 36 of variable lease costs and $ 771 of short-term lease cost.

Future lease payments under the non-cancelable operating leases as of December 31, 2023 are as follows :

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Total lease liability

Pursuant to the Company’s Third Amended and Restated Certificate of Incorporation filed in October 2019, the Company is authorized to issue 143,590,481 shares of voting common stock and 6,409,519 shares of non-voting common stock.

Holders of voting common stock shall have the exclusive right to vote for the election of directors of the Company and on all other matters requiring stockholder action.

Each share of the Company’s non-voting common stock may be converted at any time into one share of common stock at the option of its holder by providing written notice to the Company , subject to the limitations provided for in the amended and restated certificate of incorporation.

May 2023 Financing

In May 2023, the Company issued 8,337,500 shares of its common stock in an underwritten public offering, including the exercise in full by the underwriters of their option to purchase an additional 1,087,500 shares, at a public

offering price of $ 12.00 per share.

Aggregate net proceeds were $ 93,755 after deducting underwriting discounts and commissions and offering expenses of $ 6,295 .

December 2022 Financing

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Aggregate net proceeds were $ 32,562 after deducting underwriting discounts and commissions and offering expenses.

As of December 31, 2022, 271,739 pre-funded warrants had been exercised.

An additional 1,811,594 pre-funded warrants were exercised subsequent to December 31, 2022.

The pre-funded warrants were classified as a component of permanent stockholders’

equity within additional paid-in capital and were recorded at the issuance date using a relative fair value allocation method.

The pre-funded warrants are equity classified because they (i) are freestanding financial instruments that are legally detachable and separately exercisable from the equity instruments, (ii) are immediately exercisable, (iii) do not embody an obligation for the Company to repurchase its shares, (iv) permit the holders to receive a fixed number of shares of common stock upon exercise, (v) are indexed to the Company’s common stock and (vi) meet the equity classification criteria.

As of December 31, 2023, 5,045,722 pre-funded warrants had been exercised and 1,168,054 remain outstanding.

The pre-funded warrants were classified as a component of permanent stockholders’ equity within additional paid-in capital and were recorded at the issuance date using a relative fair value allocation method.

In addition, such pre-funded warrants do not provide any guarantee of value or return.

At-the-Market Offering

The Company has a Sales Agreement with Cowen and Company, LLC, to provide for the offering, issuance and sale of up to an aggregate amount of $ 75.0 million of common stock from time to time in “at-the-market”

offerings (the ATM Program) pursuant to its shelf registration statement on Form S-3 (File No.

333-250006) and subject to the limitations thereof.

During the year ended December 31, 2021, the Company sold 4,792,562 shares pursuant to the ATM Program for net proceeds of $ 48.3 million, after deducting commissions of $ 1.4 million.

No shares were sold pursuant to the ATM Program in 2022.

On March 16, 2023, the Company filed a Shelf Registration Statement in relation to the registration of common stock, preferred stock, debt securities, warrants and/or units of any combination thereof for the purposes of selling, from time to time, the Company’s common stock, debt securities or other equity securities in one or more offerings.

This S-3 was declared effective on April 26, 2023.

The Company has a Sales Agreement with Cowen and Company, LLC, or Cowen, to provide for the offering, issuance and sale of up to an aggregate amount of $ 100.0 million of common stock from time to time in “at-the-market” offerings (the ATM Program) pursuant to its shelf registration statement on Form S-3 (File No.

333-270599), which was declared effective April 26, 2023, and subject to the limitations thereof.

During the year ended December 31, 2023, the Company sold 4,760,899 shares pursuant to the ATM Program for net proceeds of $ 91,740 , after deducting commissions of $ 2,352 .

Subsequent to December 31, 2023, the Company sold 258,070 additional shares, completing the ATM Program for net proceeds of $ 5,746 , after deducting commissions of $ 147 .

On May 10, 2023, the Company delivered written notice to Cowen that it was terminating the Sales Agreement dated November 10, 2020 (the 2020 Sales Agreement), by and between the Company and Cowen.

Upon waiver of the notice period by Cowen, the termination was effective as of May 10, 2023 (the Termination Date).

All of the continuing obligations under the 2020 Sales Agreement were terminated as of the Termination Date, other than those provisions which expressly survive termination as provided in the 2020 Sales Agreement.

The Company was not subject to any termination penalties related to the termination of the 2020 Sales Agreement.

Prior to termination, 4,792,562 shares of common stock, $ 0.00001 par value per share, had been sold pursuant to the 2020 Sales Agreement.

As a result of the termination of the 2020 Sales Agreement, the Company will not offer or sell any additional shares under the 2020 Sales Agreement.

2018 Stock Option and Grant Plan

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Stock options granted under the 2018 Plan generally vest over three to four years .

There were 1,959,411 options granted under the 2018 Plan prior to the Company’s IPO in October 2019.

No further grants may be made under the 2018 Plan subsequent to the IPO.

2019 Stock Option and Incentive Plan

The 2019 Stock Option and Incentive Plan (2019 Plan) was approved by the Company’s board of directors on October 14, 2019, and became effective on October 23, 2019.

The 2019 Plan provides for the grant of incentive stock options, nonqualified stock options, stock appreciation rights, restricted stock units, restricted stock awards, unrestricted stock awards, cash-based awards and dividend equivalent rights to the Company’s officers, employees, directors and consultants.

The number of shares initially reserved for issuance under the 2019 Plan was 2,342,288 , which will be increased each January 1 thereafter by 4 % of the number of shares of the Company’s common stock outstanding on the immediately preceding December 31 or such lesser number of shares determined by the Company’s board of directors or compensation committee of the board of directors.

On January 1, 2023, the total number of shares under the 2019 Plan was increased by 1,177,805 shares.

The 2019 Stock Option and Incentive Plan (2019 Plan) was approved by the Company’s board of directors on October 14, 2019, and became effective on October 23, 2019.

The number of shares initially reserved for issuance under the 2019 Plan was 2,342,288 ,

which will be increased each January 1 thereafter by 4 % of the number of shares of the Company’s common stock outstanding on the immediately preceding December 31 or such lesser number of shares determined by the Company’s board of directors or compensation committee of the board of directors.

On June 1, 2023, at the 2023 Annual Meeting of Stockholders of the Company, the stockholders of the Company approved Amendment No.

1 to the 2019 Plan, increasing the number of shares of common stock reserved for issuance under the 2019 Plan by 3,000,000 shares.

On January 1, 2024, the total number of shares under the 2019 Plan was increased by 1,912,929 shares pursuant to the 2019 Plan Evergreen Provision.

As of December 31, 2023, there were 2,767,184 shares remaining available for issuance.

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Options Exercisable at December 31, 2023

The aggregate intrinsic value of options granted is calculated as the difference between the exercise price of the options and the estimated fair value of the Company’s common stock.

The weighted average grant-date fair value of stock options granted during the year ended December 31, 2023 and 2022 was $ 9.51 and $ 2.15 , respectively.

The fair value of each award is estimated using Black-Scholes based on the following assumptions:

For the Year Ended December 31,

Year Ended December 31,

Risk-free interest rate

1.47 %—

0.63 %—

3.38 %— 4.68 %

1.47 %— 4.18 %

Expected term

5.5 years— 6.1 years

Expected volatility

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These assumptions include:

Expected term —The expected term represents the period that stock-based awards are expected to be outstanding.

The expected term for option grants is determined using the simplified method, which is the midpoint between the vesting period and the contractual term of the option.

Expected volatility —As a privately held company prior to the Company’s IPO in October 2019, the Company has limited trading history for its common stock and, as such, the expected volatility is estimated based on the average volatility for comparable publicly traded biotechnology companies over a period equal to the expected term of the stock-based awards.

Expected volatility —As a privately held company prior to the Company’s IPO in October 2019, the Company has limited trading history for its common stock and, as such, the expected volatility is estimated based on a weighted average volatility for the Company's stock price and comparable publicly traded biotechnology companies over a period equal to the expected term of the stock-based awards.

The comparable companies were chosen based on their similar size, stage in the life cycle or area of specialty.

The Company will continue to apply this process until a sufficient amount of historical information regarding the volatility of its own stock price becomes available.

Risk-free interest rate —The risk-free interest rate is based on the U.S.

Treasury zero coupon issues in effect at the time of grant for periods corresponding with the expected term of a stock-based award.

Expected dividend —The Company has never paid dividends on its common stock and has no plans to pay dividends on its common stock.

Therefore, the Company used an expected dividend yield of zero.

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The Company has recorded stock-based compensation in the accompanying statements of operations as follows:

For the Year Ended December 31,

Research and development

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2019 Employee Stock Purchase Plan

The 2019 Employee Stock Purchase Plan (2019 ESPP) was approved by the Company’s board of directors on October 14, 2019, and became effective on October 23, 2019.

A total of 234,229 shares of common stock were initially reserved for issuance under the 2019 ESPP, and will be increased each January 1 thereafter through January 1, 2029 by the least of (i) 234,229 shares of common stock, (ii) 1 % of the number of shares of the Company’s common stock outstanding on the immediately preceding December 31 or (iii) such lesser number of shares determined by the 2019 ESPP’s administrator.

The 2019 Employee Stock Purchase Plan (2019 ESPP) was approved by the Company’s board of directors on October 14, 2019, and became effective on October 23, 2019.

On January 1, 2024, there was no increase to the total number of shares under the 2019 ESPP.

As of December 31, 2023, there were 372,315 shares remaining available for issuance.

Employee contributions are made through payroll deductions of up to 15 % of eligible compensation over the offering period.

A participant may not accrue rights to purchase more than $ 25 worth of the Company’s common stock for each calendar year in which such right is outstanding.

At the end of each offering period, shares of the Company’s common stock may be purchased at 85 % of the lesser of the Company’s common stock on (i) the first trading day of the relevant offering period and (ii) the last trading day of the relevant offering period.

A participant may not accrue rights to purchase more than $ 25 worth of the Company’s common stock for each calendar year in which such right is outstanding.

The first offering period commenced on July 1, 2020 and ended on November 30, 2020.

Thereafter, offerings will be six months in duration and will commence on each December 1 and June 1.

The reconciliation of federal statutory income tax rate to the Company’s effective income tax rate is as follows:

For the Year Ended December 31,

The reconciliation of federal statutory income tax rate to the Company’s effective income tax rate is as follows:

Year Ended December 31,

Expected income tax benefit at the federal statutory rate

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Non-deductible items and other

Change in state tax rate

Change in state and local tax rate

Change in valuation allowance

Deferred income taxes reflect the net effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes.

The principal components of the Company’s deferred tax assets and liabilities consisted of the following:

Deferred tax assets:

Federal, state and local net operating loss carryforwards

Research and development tax credits

Capitalized research and development costs

Research and development tax credits

Stock-based compensation deductions

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Deferred tax liabilities:

Operating lease assets

Operating lease right-of-use assets

Net deferred tax assets

The Company increased its valuation allowance by $ 22,871 for the year ended December 31, 2023 in order to maintain a full valuation allowance against its deferred tax assets.

Based on the Company’s history of losses, the Company recorded a full valuation allowance against its deferred tax assets as of December 31, 2022.

intends to maintain a valuation allowance until sufficient positive evidence exists to support a reversal of the allowance.

Based on the Company’s history of losses, the Company recorded a full valuation allowance against its deferred tax assets as of December 31, 2023.

The Company intends to maintain a valuation allowance until sufficient positive evidence exists to support a reversal of the allowance.

As of December 31, 2023, the Company had federal, state and local net operating loss carryforwards of $ 121,570 , $ 131,901 and $ 82,957 , respectively;

$ 98,924 of the federal amounts do not expire, and the remaining $ 250 expire in 2037 .

$ 121,320 of the federal net operating losses do not expire, and the remaining $ 250 expire in 2037 .

The state net operating losses begin to expire in 2037 .

The local net operating losses begin to expire in 2023 .

The local net operating losses began to expire in 2024 .

As of December 31, 2023, the Company had federal and state research and development tax credit carryforwards of $ 9,923 and $ 269 , respectively, which begin to expire in 2038 .

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The Company evaluates tax positions for recognition using a more-likely-than-not recognition threshold, and those tax positions eligible for recognition are measured as the largest amount of tax benefit that is greater than 50 % likely of being realized upon the effective settlement with a taxing authority that has full knowledge of all relevant information.

As of December 31, 2022, the Company had no unrecognized income tax benefits that would affect the Company’s effective tax rate if recognized.

As of December 31, 2023, the Company had no unrecognized income tax benefits that would affect the Company’s effective tax rate if recognized.

Net Loss Per Share

The Company calculates basic and diluted net loss per share attributable to common stockholders in conformity with the two-class method required for participating securities.

The Company calculates basic and diluted net loss per share in conformity with the two-class method required for participating securities.

For the years ended December 31, 2023 and 2022, the Company had voting and non-voting common stock outstanding.

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Basic net loss per share of common stock is computed by dividing the net loss per share of common stock by the weighted average number of shares of common stock outstanding for the period.

The weighted-average shares of common stock outstanding as of December 31, 2022 included outstanding pre-funded warrants to purchase up to an aggregate of 5,942,036 shares of common stock.

The weighted-average shares of common stock outstanding as of December 31, 2023 and 2022 included outstanding pre-funded warrants to purchase up to an aggregate of 1,168,054 and 5,942,036 shares of common stock, respectively.

Diluted net loss per share is calculated using the if-converted method, which assumes conversion of all non-voting common stock to voting common stock.

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Basic net loss per share:

Allocation of undistributed losses attributable to common stockholders

Allocation of undistributed losses

Weighted average number of shares used in basic per share computation

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Basic net loss per share:

Allocation of undistributed losses attributable to common stockholders

Allocation of undistributed losses

Weighted average number of shares used in basic per share computation

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The following outstanding potentially dilutive shares have been excluded from the calculation of diluted net loss per share, as their effect is anti-dilutive:

For the Year Ended December 31,

As of December 31,

Stock options to purchase common stock

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The 401(k) Plan covers all employees who meet defined minimum age and service requirements and allows participants to defer a portion of their annual compensation on a pretax basis.

Effective January 1, 2020, the Plan provided for matching contributions on a portion of participant contributions pursuant to the 401(k) Savings Plan’s matching formula, up to 4 % of eligible compensation.

All matching contributions and participant contributions vest immediately.

Contributions totaled $ 521 and $ 351 for the years ended December 31, 2023 and 2022, respectively, and have been recorded in the statements of operations.

Subsequent Event

In January 2023, the Company entered into an Option and License Agreement (Autolus Agreement) with Autolus Holdings (UK) Limited (Autolus), wherein the Autolus Agreement grants the Company a non-exclusive license to access Autolus' RQR8 technology in its CD19-CAR T cell therapy program, and subject to additional nominal option exercise fees, up to four additional targets.

Under the terms of the Autolus Agreement, the Company is required to pay Autolus an upfront license fee of $ 1,200 , of which $ 800 was paid in February 2023 and $ 100 will be paid at the end of each calendar quarter in 2023.

The Company can terminate the Autolus Agreement at will upon advance written notice.

Each of the Company and Autolus may terminate the Agreement for a material, uncured breach or insolvency of the other party.

EXHIBIT INDEX

Third Amended and Restated Certificate of Incorporation of the Registrant, as currently in effect (incorporated by reference to Exhibit 3.1 of the Registrant’s Current Report on Form 8-K (File No.

001-39103) filed on October 30, 2019)

Amended and Restated Bylaws of the Registrant, as currently in effect (incorporated by reference to Exhibit 3.2 of the Registrant’s Current Report on Form 8-K (File No.

001-39103) filed on October 30, 2019)

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001-39103) filed with the SEC on May 12, 2022)

Specimen Common Stock Certificate (incorporated by reference to Exhibit 4.1 of the Registrant’s Registration Statement on Form S-1 (File No.

333-234017) filed on October 16, 2019 )

Amended and Restated Investors' Rights Agreement among the Registrant and certain of its stockholders, dated January 2, 2019 (incorporated by reference to Exhibit 4.2 of the Registrant’s Registration Statement on Form S-1 (File No.

333-234017) filed on September 30, 2019)

Description of Securities

2018 Stock Option and Grant Plan, as amended, and form of award agreements thereunder (incorporated by reference to Exhibit 10.1 of the Registrant’s Registration Statement on Form S-1 (File No.

Form of Pre-Funded Warrant (incorporated by reference to Exhibit 4.1 of the Registrant's Current Report on Form 8-K (File No.

001-39103) filed with the SEC on December 12, 2022

2018 Stock Option and Grant Plan, as amended, and form of award agreements thereunder (incorporated by reference to Exhibit 10.1 of the Registrant’s Registration Statement on Form S-1 (File No.

333-234017) filed on September 30, 2019)

2019 Stock Option and Incentive Plan, and form of award agreements thereunder.

(incorporated by reference to Exhibit 10.2 of the Registrant’s Registration Statement on Form S-1/A (File No.

333-234017) filed on October 16, 2019)

Amendment No.

1 to the Cabaletta Bio, Inc.

2019 Stock Option and Incentive Plan (incorporated by reference to Exhibit 10.1 to the Current Report on Form 8-K filed on June 1, 2023)

2019 Employee Stock Purchase Plan.

(incorporated by reference to Exhibit 10.3 of the Registrant’s Registration Statement on Form S-1/A (File No.

333-234017) filed on October 16, 2019)

Senior Executive Cash Incentive Bonus Plan (incorporated by reference to Exhibit 10.4 of the Registrant’s Quarterly Report on Form 10-Q filed on December 5, 2019)

Form of Indemnification Agreement between the Registrant and each of its directors (incorporated by reference to Exhibit 10.5 of the Registrant’s Registration Statement on Form S-1, filed with the SEC on September 30, 2019)

Form of Indemnification Agreement between the Registrant and each of its executive officers (incorporated by reference to Exhibit 10.4 of the Registrant’s Registration Statement on Form S-1, filed with the SEC on September 30, 2019)

Amended and Restated License Agreement, dated as of July 23, 2019, among the Registrant, the Trustees of the University of Pennsylvania and the Children’s Hospital of Philadelphia (incorporated by reference to Exhibit 10.6 to the Registrant’s Registration Statement on Form S-1, filed with the SEC on September 30, 2019)

Sponsored Research Agreement, dated as of April 23, 2018, between the Registrant and the Trustees of the University of Pennsylvania (incorporated by reference to Exhibit 10.7 to the Registrant’s Registration Statement on Form S-1, filed with the SEC on September 30, 2019)

Sponsored Research Agreement, dated as of April 23, 2018, between the Registrant and the Trustees of the University of Pennsylvania (incorporated by reference to Exhibit 10.8 to the Registrant’s Registration Statement on Form S-1, filed with the SEC on September 30, 2019)

Master Translational Research Services Agreement, dated as of October 2018, between the Registrant and the Trustees of the University of Pennsylvania (incorporated by reference to Exhibit 10.9 to the Registrant’s Registration Statement on Form S-1, filed with the SEC on September 30, 2019)

CAROT Master Services Addendum to Master Translational Research Services Agreement, dated as of February 4, 2019, between the Registrant and the Trustees of the University of Pennsylvania (incorporated by reference to Exhibit 10.10 to the Registrant’s Registration Statement on Form S-1, filed with the SEC on September 30, 2019)

CVPF Master Services Addendum to Master Translational Research Services Agreement, dated as of October 22, 2018, between the Registrant and the Trustees of the University of Pennsylvania (incorporated by reference to Exhibit 10.11 to the Registrant’s Registration Statement on Form S-1, filed with the SEC on September 30, 2019)

Senior Executive Cash Incentive Bonus Plan (incorporated by reference to Exhibit 10.4 of the Registrant’s Quarterly Report on Form 10-Q filed on December 5, 2019)

to Exhibit 10.6 to the Registrant’s Registration Statement on Form S-1, filed with the SEC on September 30, 2019)

Lease, dated as of February 11, 2019, between the Registrant and Brandywine Cira, L.P.

(incorporated by reference to Exhibit 10.13 to the Registrant’s Registration Statement on Form S-1, filed with the SEC on September 30, 2019)

Employment Agreement between the Registrant and Steven Nichtberger (incorporated by reference to Exhibit 10.16 to the Registrant’s Registration Statement on Form S-1, filed with the SEC on September 30, 2019)

Employment Agreement between the Registrant and Anup Marda (incorporated by reference to Exhibit 10.17 to the Registrant’s Registration Statement on Form S-1, filed with the SEC on September 30, 2019)

Employment Agreement between the Registrant and Gwendolyn Binder (incorporated by reference to Exhibit 10.18 to the Registrant’s Registration Statement on Form S-1, filed with the SEC on September 30, 2019)

Employment Agreement between the Registrant and David Chang (incorporated by reference to Exhibit 10.19 to the Registrant’s Registration Statement on Form S-1, filed with the SEC on September 30, 2019)

Amended and Restated Non-Employee Director Compensation Policy (incorporated by reference to Exhibit 10.18 to the Registrant’s Annual Report on Form 10-K (File No.

001-39103) filed on March 17, 2022)

(incorporated by reference to Exhibit 10.13 to the Registrant’s Registration Statement on Form S-1, filed with the SEC on September 30, 2019)

Third Amended and Restated Non-Employee Director Compensation Policy

Amendment No.

1, dated May 27, 2020, to the Sponsored Research Agreement, dated April 23, 2018, between the Registrant and the Trustees of the University of Pennsylvania (incorporated by reference to Exhibit 10.1 to the Registrant’s Current Report on Form 8-K (File No.

001-39103) filed on May 28, 2020)

First Amendment, dated May 27, 2020, to the Amended and Restated License Agreement, dated July 23, 2019, among the Registrant, the Trustees of the University of Pennsylvania and the Children’s Hospital of Philadelphia (incorporated by reference to Exhibit 10.2 to the Registrant’s Current Report on Form 8-K (File No.

001-39103) filed on May 28, 2020)

Amendment to CAROT Master Services Addendum to Master Translational Research Services Agreement, dated as of May 18, 2020 between the Registrant and the Trustees of the University of Pennsylvania (incorporated by reference to Exhibit 10.1 to the Registrant’s Quarterly Report on Form 10-Q (File No.

Amendment to CAROT Master Services Addendum to Master Translational Research Services Agreement, dated as of May 18, 2020 between the Registrant and the Trustees of the University of

Pennsylvania (incorporated by reference to Exhibit 10.1 to the Registrant’s Quarterly Report on Form 10-Q (File No.

001-39103) filed on August 6, 2020)

1 unchanged sentence

2, dated August 17, 2020, to the Sponsored Research Agreement, dated April 23, 2018, as amended by Amendment No.

1 dated May 27, 2020, between the Registrant and the Trustees of the

University of Pennsylvania (incorporated by reference to Exhibit 10.1 to the Registrant’s Quarterly Report on Form 10-Q (File No.

1 dated May 27, 2020, between the Registrant and the Trustees of the University of Pennsylvania (incorporated by reference to Exhibit 10.1 to the Registrant’s Quarterly Report on Form 10-Q (File No.

001-39103) filed on November 10, 2020)

Amendment No.

1, dated April 27, 2021, to the Sponsored Research Agreement, dated April 23, 2018, between the Registrant and the Trustees of the University of Pennsylvania (incorporated by reference to Exhibit 10.1 to the Registrant’s Quarterly Report on Form 10-Q (File No.

001-39103) filed on May 3, 2021 )

Amendment No.

2, dated October 19, 2021, to the Sponsored Research Agreement, dated April 23, 2018, between the Registrant and the Trustees of the University of Pennsylvania (incorporated by reference to Exhibit 10.1 to the Registrant’s Quarterly Report on Form 10-Q (File No.

001-39103) filed on November 1, 2021 )

Second Amendment, dated October 19, 2021, to the First Amended and Restated License Agreement, dated May 27, 2020, among the Registrant, the Trustees of the University of Pennsylvania and the Children’s Hospital of Philadelphia (incorporated by reference to Exhibit 10.1 to the Registrant’s Quarterly Report on Form 10-Q (File No.

001-39103) filed on November 1, 2021)

First Amendment, dated February 15, 2022, to the Lease, dated as of February 11, 2019, between the Registrant and Brandywine Cira, L.P.

(incorporated by reference to Exhibit 10.26 to the Registrant’s Annual Report on Form 10-K (File No.

001-39103) filed on March 17, 2022)

Amendment No.

3, dated December 17, 2021, to the Sponsored Research Agreement, dated April 23, 2018, between the Registrant and the Trustees of the University of Pennsylvania (incorporated by reference to Exhibit 10.27 to the Registrant’s Annual Report on Form 10-K (File No.

001-39103) filed on March 17, 2022)

Form of Employment Agreement (incorporated by reference to Exhibit 10.28 to the Registrant’s Annual Report on Form 10-K (File No.

Amendment No.

4, dated December 1, 2022, to the Sponsored Research Agreement, dated April 23, 2018, between the Registrant and the Trustees of the University of Pennsylvania (incorporated by reference to Exhibit 10.33 to the Registrant’s Annual Report on Form 10-K (File No.

001-39103) filed on March 16, 2023)

Sponsored Research Agreement, dated as of December 23, 2021, between the Registrant and the Trustees of the University of Pennsylvania (incorporated by reference to Exhibit 10.29 to the Registrant’s Annual Report on Form 10-K (File No.

Amendment No.

5, dated July 25, 2023, to the Sponsored Research Agreement, dated April 23, 2018, between the Registrant and the Trustees of the University of Pennsylvania (incorporated by reference to Exhibit 10.2 to the Registrant’s Quarterly Report on Form 10-Q (File No.

001-39103) filed on November 9, 2023)

Form of Employment Agreement (incorporated by reference to Exhibit 10.28 to the Registrant’s Annual Report on Form 10-K (File No.

001-39103) filed on March 17, 2022)

Option Agreement, dated December 23, 2021, by and between the Registrant and the Trustees of the University of Pennsylvania (incorporated by reference to Exhibit 10.30 to the Registrant’s Annual Report on Form 10-K (File No.

001-39103) filed on March 17, 2022)

Licence and Supply Agreement, dated December 30, 2021, by and between the Registrant and Oxford Biomedica (UK) Limited (incorporated by reference to Exhibit 10.31 to the Registrant’s Annual Report on Form 10-K (File No.

001-39103) filed on March 17, 2022)

Exclusive License Agreement, dated October 7, 2022, by and between the Registrant and Nanjing IASO Biotherapeutics Co., LTD.(incorporated by reference to Exhibit 10.31 to the Registrant’s Quarterly Report on Form 10-Q (File No.

001-39103) filed on March 17, 2022)

First Amendment to the Licence and Supply Agreement, dated as of May 2, 2023, between the Registrant and Oxford Biomedica (UK) Limited (incorporated by reference to Exhibit 10.2 to the Registrant’s Quarterly Report on Form 10-Q (File No.

001-39103) filed on August 10, 2023)

Second Amendment to the Licence and Supply Agreement, dated as of August 18, 2023, between the Registrant and Oxford Biomedica (UK) Limited (incorporated by reference to Exhibit 10.1 to the Registrant’s Quarterly Report on Form 10-Q (File No.

001-39103) filed on November 9, 2023)

Amendment No.

4, dated December 1, 2022, to the Sponsored Research Agreement, dated April 23, 2018, between the Registrant and the Trustees of the University of Pennsylvania

Development, Manufacturing, and Testing Services Agreement, dated January 11, 2021, between the Registrant and WuXi Advanced Therapies Inc.

001-39103) filed on November 10, 2022 )

Development, Manufacturing, and Testing Services Agreement, dated January 11, 2021, between the Registrant and WuXi Advanced Therapies Inc.(incorporated by reference to Exhibit 10.34 to the Registrant’s Annual Report on Form 10-K (File No.

001-39103) filed on March 16, 2023)

Master Translational Research Services Agreement, dated as of February 9, 2023, between the Registrant and the Trustees of the University of Pennsylvania (incorporated by reference to Exhibit 10.1 to the Registrant's Quarterly Report on Form 10-Q (File No.

001-39103) filed on May 11, 2023)

List of Subsidiaries of the Registrant

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Section 1350, as adopted Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002

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the instance document does not appear in the Interactive Data File because its XBRL tags are embedded within the Inline XBRL document

Cabaletta Bio, Inc.'s Compensation Recovery Policy

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Inline XBRL Taxonomy Extension Schema Document

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* Filed herewith.

** The certifications furnished in Exhibit 32.1 and 32.2 hereto are deemed to accompany this Annual Report on Form 10-K and will not be deemed “filed”

for purposes of Section 18 of the Securities Exchange Act of 1934, as amended.

** The certifications furnished in Exhibit 32.1 and 32.2 hereto are deemed to accompany this Annual Report on Form 10-K and will not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended.

Such certifications will not be deemed to be incorporated by reference into any filings under the Securities Act of 1933, as amended, or the Securities Exchange Act of 1934, as amended, except to the extent that the Registrant specifically incorporates it by reference.

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March 21, 2024

/s/ Shawn Tomasello

March 21, 2024

Shawn Tomasello

Compared sentence by sentence after normalising whitespace, quotation marks, case and digits, so re-formatting and restated figures do not read as changed language. Wording changes appear as one removal and one addition. The current filing and the prior one are authoritative.

What changed 10-K

Item 9A. Controls and Procedures