Zenas BioPharma, Inc. 10-Q

Item 1. Financial Statements Zenas BioPharma, Inc. Condensed Consolidated Balance Sheets (Unaudited) (in thousands, except share and per share amounts) ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ December 31, ​ 2025 2024 Assets ​ ​ ​ ​ ​ Current assets: ​ ​ ​ ​ ​ ​ Cash and cash equivalents ​ $ 115,565 ​ $ 319,742 Short-term investments ​ ​ 175,319 ​ ​ 31,024 Restricted cash ​ ​ — ​ ​ 90 Prepaid expenses and other current assets ​ ​ 5,758 ​ ​ 5,067 Total current assets ​ ​ 296,642 ​ ​ 355,923 Property and equipment, net ​ ​ 50 ​ ​ 185 Operating lease right-of-use assets, net ​ ​ 807 ​ ​ 1,004 Long-term investments ​ ​ 10,717 ​ ​ — Other non-current assets ​ ​ 13,802 ​ ​ 12,856 Total assets ​ $ 322,018 ​ $ 369,968 Liabilities and Stockholders’ Equity ​ ​ ​ ​ ​ ​ Current liabilities: ​ ​ ​ ​ ​ ​ Accounts payable ​ $ 6,444 ​ $ 17,136 Accrued expenses ​ ​ 45,359 ​ ​ 39,371 Operating lease liabilities, current ​ ​ 618 ​ ​ 785 Total current liabilities ​ ​ 52,421 ​ ​ 57,292 Long-term liabilities: ​ ​ ​ ​ ​ ​ Royalty obligation ​ ​ 72,989 ​ ​ — Operating lease liabilities, less current portion ​ ​ 180 ​ ​ 218 Total long-term liabilities ​ ​ 73,169 ​ ​ 218 Total liabilities ​ ​ 125,590 ​ ​ 57,510 Commitments and contingencies (Note 13) ​ ​ ​ ​ ​ ​ Stockholders’ equity: ​ ​ ​ ​ ​ ​ Preferred stock, par value $ 0.0001 per share; 25,000,000 shares authorized and no shares issued and outstanding as of September 30, 2025 and December 31, 2024 ​ ​ — ​ ​ — Common stock, par value $ 0.0001 per share; 175,000,000 shares authorized; 42,213,465 and 41,793,412 shares issued and outstanding as of September 30, 2025 and December 31, 2024, respectively ​ ​ 4 ​ ​ 4 Additional paid-in capital ​ ​ 721,179 ​ ​ 699,651 Accumulated other comprehensive (loss) income ​ ​ ( 69 ) ​ ​ 194 Accumulated deficit ​ ​ ( 524,686 ) ​ ​ ( 387,391 ) Total stockholders’ equity ​ ​ 196,428 ​ ​ 312,458 Total liabilities and stockholders’ equity ​ $ 322,018 ​ $ 369,968 ​ ​ The accompanying notes are an integral part of these condensed consolidated financial statements. ​ 7 Table of Contents Zenas BioPharma, Inc. Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) (in thousands, except share and per share amounts) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the three months ended September 30, ​ ​ For the nine months ended September 30, ​ ​ 2025 ​ ​ 2024 ​ ​ 2025 ​ ​ 2024 Revenue: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ License and collaboration revenue $ — ​ $ — ​ $ 10,000 ​ $ — Total revenue ​ — ​ ​ — ​ ​ 10,000 ​ ​ — Operating expenses: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Research and development ​ 34,402 ​ ​ 33,530 ​ ​ 112,343 ​ ​ 89,982 General and administrative ​ 13,178 ​ ​ 7,454 ​ ​ 37,730 ​ ​ 18,283 Acquired in-process research and development ​ 5,000 ​ ​ — ​ ​ 5,000 ​ ​ — Total operating expenses ​ 52,580 ​ ​ 40,984 ​ ​ 155,073 ​ ​ 108,265 Loss from operations ​ ( 52,580 ) ​ ​ ( 40,984 ) ​ ​ ( 145,073 ) ​ ​ ( 108,265 ) Other income (expense), net: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair value adjustments to convertible notes ​ — ​ ​ — ​ ​ — ​ ​ ( 846 ) Other income, net ​ 1,081 ​ ​ 2,378 ​ ​ 7,593 ​ ​ 4,727 Total other income (expense), net ​ 1,081 ​ ​ 2,378 ​ ​ 7,593 ​ ​ 3,881 Loss before income taxes ​ ( 51,499 ) ​ ​ ( 38,606 ) ​ ​ ( 137,480 ) ​ ​ ( 104,384 ) Income tax (provision) benefit ​ — ​ ​ — ​ ​ 185 ​ ​ — Net loss to common stockholders $ ( 51,499 ) ​ $ ( 38,606 ) ​ $ ( 137,295 ) ​ $ ( 104,384 ) Net loss per share attributable to common stockholders - basic and diluted $ ( 1.22 ) ​ $ ( 5.02 ) ​ $ ( 3.27 ) ​ $ ( 28.83 ) Weighted-average common stock outstanding - basic and diluted ​ 42,159,340 ​ ​ 7,697,695 ​ ​ 41,943,160 ​ ​ 3,621,276 Comprehensive loss: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss to common stockholders $ ( 51,499 ) ​ $ ( 38,606 ) ​ $ ( 137,295 ) ​ $ ( 104,384 ) Other comprehensive income (loss): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrealized gain on investments ​ 35 ​ ​ — ​ ​ 77 ​ ​ — Foreign currency translation adjustment ​ ( 10 ) ​ ​ ( 50 ) ​ ​ ( 340 ) ​ ​ 16 Comprehensive loss $ ( 51,474 ) ​ $ ( 38,656 ) ​ $ ( 137,558 ) ​ $ ( 104,368 ) ​ ​ The accompanying notes are an integral part of these condensed consolidated financial statements. ​ ​ 8 Table of Contents Zenas BioPharma, Inc. Condensed Consolidated Statements of Stockholders’ Equity (Deficit) (Unaudited) (in thousands, except share data) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Common Stock ​ ​ ​ ​ ​ ​ ​ ​ ​ Shares Amount Additional Paid-in Capital Accumulated Other Comprehensive Income (Loss) Accumulated Deficit Total Stockholders' Equity Balance as of December 31, 2024 ​ 41,793,412 ​ $ 4 ​ $ 699,651 ​ $ 194 ​ $ ( 387,391 ) ​ $ 312,458 Exercises of common stock options ​ 28,475 ​ ​ — ​ ​ 99 ​ ​ — ​ ​ — ​ ​ 99 Stock-based compensation expense ​ — ​ ​ — ​ ​ 5,386 ​ ​ — ​ ​ — ​ ​ 5,386 Unrealized gain on investments ​ — ​ ​ — ​ ​ — ​ ​ 12 ​ ​ — ​ ​ 12 Foreign currency translation adjustment ​ — ​ ​ — ​ ​ — ​ ​ ( 65 ) ​ ​ — ​ ​ ( 65 ) Net loss ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ ( 33,573 ) ​ ​ ( 33,573 ) Balance as of March 31, 2025 ​ 41,821,887 ​ $ 4 ​ $ 705,136 ​ $ 141 ​ $ ( 420,964 ) ​ $ 284,317 Exercises of common stock options ​ 266,810 ​ ​ — ​ ​ 1,722 ​ ​ — ​ ​ — ​ ​ 1,722 Stock-based compensation expense ​ — ​ ​ — ​ ​ 6,045 ​ ​ — ​ ​ — ​ ​ 6,045 Unrealized gain on investments ​ — ​ ​ — ​ ​ — ​ ​ 30 ​ ​ — ​ ​ 30 Foreign currency translation adjustment ​ — ​ ​ — ​ ​ — ​ ​ ( 265 ) ​ ​ — ​ ​ ( 265 ) Net loss ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ ( 52,223 ) ​ ​ ( 52,223 ) Balance as of June 30, 2025 ​ 42,088,697 ​ $ 4 ​ $ 712,903 ​ $ ( 94 ) ​ $ ( 473,187 ) ​ $ 239,626 Exercises of common stock options ​ 82,000 ​ ​ — ​ ​ 664 ​ ​ — ​ ​ — ​ ​ 664 Stock-based compensation expense ​ — ​ ​ — ​ ​ 7,336 ​ ​ — ​ ​ — ​ ​ 7,336 Purchases of common stock under the Employee Stock Purchase Plan ​ 42,768 ​ ​ — ​ ​ 276 ​ ​ — ​ ​ — ​ ​ 276 Unrealized gain on investments ​ — ​ ​ — ​ ​ — ​ ​ 35 ​ ​ — ​ ​ 35 Foreign currency translation adjustment ​ — ​ ​ — ​ ​ — ​ ​ ( 10 ) ​ ​ — ​ ​ ( 10 ) Net loss ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ ( 51,499 ) ​ ​ ( 51,499 ) Balance as of September 30, 2025 ​ 42,213,465 ​ $ 4 ​ $ 721,179 ​ $ ( 69 ) ​ $ ( 524,686 ) ​ $ 196,428 ​ The accompanying notes are an integral part of these condensed consolidated financial statements. ​ ​ 9 Table of Contents Zenas BioPharma, Inc. Condensed Consolidated Statements of Stockholders’ Equity (Deficit) (Unaudited) (in thousands, except share data) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Convertible Preferred Stock ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Seed Series ​ Series A ​ Series B ​ Series C ​ ​ Common Stock ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Shares Amount Shares Amount Shares Amount Shares Amount ​ Shares Amount Additional Paid-in Capital Accumulated Other Comprehensive Income Accumulated Deficit Total Stockholders' Equity (Deficit) Balance as of December 31, 2023 ​ ​ 1,785,714 ​ $ 956 ​ 17,589,380 ​ $ 55,840 ​ 81,242,587 ​ $ 193,290 ​ — ​ $ — ​ ​ 1,576,854 ​ $ — ​ $ 4,645 ​ $ 37 ​ $ ( 230,403 ) ​ $ ( 225,721 ) Repurchase of unvested restricted stock awards ​ ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ ​ ( 21,172 ) ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — Exercises of common stock options ​ ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ ​ 7,035 ​ ​ — ​ ​ 42 ​ ​ — ​ ​ — ​ ​ 42 Stock-based compensation expense ​ ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ 947 ​ ​ — ​ ​ — ​ ​ 947 Foreign currency translation adjustment ​ ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ 37 ​ ​ — ​ ​ 37 Net loss ​ ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ ( 27,800 ) ​ ​ ( 27,800 ) Balance as of March 31, 2024 ​ ​ 1,785,714 ​ $ 956 ​ 17,589,380 ​ $ 55,840 ​ 81,242,587 ​ $ 193,290 ​ — ​ $ — ​ ​ 1,562,717 ​ $ — ​ $ 5,634 ​ $ 74 ​ $ ( 258,203 ) ​ $ ( 252,495 ) Issuance of Series C convertible preferred stock, net of $ 619 issuance cost ​ ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ 116,275,239 ​ ​ 199,526 ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — Exercises of common stock options ​ ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ ​ 15,655 ​ ​ — ​ ​ 124 ​ ​ — ​ ​ — ​ ​ 124 Stock-based compensation expense ​ ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ 1,536 ​ ​ — ​ ​ — ​ ​ 1,536 Foreign currency translation adjustment ​ ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ 30 ​ ​ — ​ ​ 30 Net loss ​ ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ ( 37,977 ) ​ ​ ( 37,977 ) Balance as of June 30, 2024 ​ ​ 1,785,714 ​ $ 956 ​ 17,589,380 ​ $ 55,840 ​ 81,242,587 ​ $ 193,290 ​ 116,275,239 ​ $ 199,526 ​ ​ 1,578,372 ​ $ — ​ $ 7,294 ​ $ 104 ​ $ ( 296,180 ) ​ $ ( 288,782 ) Conversion of convertible preferred stock upon closing of initial public offering ​ ​ ( 1,785,714 ) ​ ​ ( 956 ) ​ ( 17,589,380 ) ​ ​ ( 55,840 ) ​ ( 81,242,587 ) ​ ​ ( 193,290 ) ​ ( 116,275,239 ) ​ ​ ( 199,526 ) ​ ​ 24,978,715 ​ ​ 2 ​ ​ 449,610 ​ ​ — ​ ​ — ​ ​ 449,612 Issuance of common stock from initial public offer, net of underwriting discounts, commissions and other issuance costs ​ ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ ​ 15,220,588 ​ ​ 2 ​ ​ 234,384 ​ ​ — ​ ​ — ​ ​ 234,386 Exercises of common stock options ​ ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ ​ 3,263 ​ ​ — ​ ​ 32 ​ ​ — ​ ​ — ​ ​ 32 Stock-based compensation expense ​ ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ 2,843 ​ ​ — ​ ​ — ​ ​ 2,843 Foreign currency translation adjustment ​ ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ ( 50 ) ​ ​ — ​ ​ ( 50 ) Net loss ​ ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ — ​ ​ ( 38,606 ) ​ ​ ( 38,606 ) Balance as of September 30, 2024 ​ ​ — ​ $ — ​ — ​ $ — ​ — ​ $ — ​ — ​ $ — ​ ​ 41,780,938 ​ $ 4 ​ $ 694,163 ​ $ 54 ​ $ ( 334,786 ) ​ $ 359,435 ​ The accompanying notes are an integral part of these condensed consolidated financial statements. ​ 10 ​ Zenas BioPharma, Inc. Condensed Consolidated Statements of Cash Flows (Unaudited) (in thousands) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, ​ ​ 2025 ​ 2024 Cash flows from operating activities: ​ ​ ​ ​ ​ ​ Net loss ​ $ ( 137,295 ) ​ $ ( 104,384 ) Adjustments to reconcile net loss to net cash used in operating activities: ​ ​ ​ ​ ​ ​ Acquired in-process research and development ​ ​ 5,000 ​ ​ — Depreciation expense ​ ​ 46 ​ ​ 104 Loss on disposal of property and equipment ​ ​ 107 ​ ​ — Net amortization of premiums and accretion of discounts on investments ​ ​ ( 1,510 ) ​ ​ — Non-cash interest expense on royalty obligation ​ ​ 1,679 ​ ​ — Stock-based compensation expense ​ ​ 18,767 ​ ​ 5,326 Change in fair value of convertible notes ​ ​ — ​ ​ 846 Non-cash lease expense ​ ​ 651 ​ ​ 423 Changes in operating assets and liabilities: ​ ​ ​ ​ ​ ​ Prepaid expenses and other assets ​ ​ ( 799 ) ​ ​ 475 Accounts payable ​ ​ ( 11,159 ) ​ ​ 6,319 Accrued expenses ​ ​ 5,251 ​ ​ 10,200 Operating lease liabilities ​ ​ ( 657 ) ​ ​ ( 429 ) Net cash used in operating activities ​ ​ ( 119,919 ) ​ ​ ( 81,120 ) Cash flows from investing activities: ​ ​ ​ ​ ​ ​ Purchases of property and equipment ​ ​ ( 18 ) ​ ​ ( 57 ) Purchases of investments ​ ​ ( 284,862 ) ​ ​ ( 26,760 ) Proceeds from sales and maturities of investments ​ ​ 131,358 ​ ​ — Product candidate license acquisitions ​ ​ ( 5,000 ) ​ ​ — Net cash used in investing activities ​ ​ ( 158,522 ) ​ ​ ( 26,817 ) Cash flows from financing activities: ​ ​ ​ ​ ​ ​ Proceeds from issuance of Series C convertible preferred stock, net of issuance costs ​ ​ — ​ ​ 178,381 Payment of initial public offering costs ​ ​ — ​ ​ ( 1,861 ) Payment of deferred offering costs ​ ​ ( 3,324 ) ​ ​ — Proceeds from royalty obligation ​ ​ 75,000 ​ ​ — Proceeds from exercise of stock options ​ ​ 2,485 ​ ​ 198 Proceeds from issuance of common stock under employee stock purchase plan ​ ​ 276 ​ ​ — Proceeds from initial public offering, net of underwriting discount and commissions ​ ​ — ​ ​ 234,387 Net cash provided by financing activities ​ ​ 74,437 ​ ​ 411,105 Effect of exchange rate changes on cash, cash equivalents and restricted cash ​ ​ ( 263 ) ​ ​ 16 Net (decrease) increase in cash, cash equivalents and restricted cash ​ ​ ( 204,267 ) ​ ​ 303,184 Cash, cash equivalents and restricted cash at beginning of period ​ ​ 319,832 ​ ​ 56,943 Cash, cash equivalents and restricted cash at end of period ​ $ 115,565 ​ $ 360,127 ​ ​ ​ ​ ​ ​ ​ Supplemental disclosure of non-cash investing and financing activities: ​ ​ ​ ​ ​ ​ Right-of-use assets obtained under operating lease arrangements ​ $ 445 ​ $ — Conversion of BMS Note into Series C convertible preferred stock ​ $ — ​ $ 21,146 Deferred offering costs in accounts payable and accrued expenses ​ $ 1,204 ​ $ 4,389 ​ ​ ​ ​ ​ ​ ​ Reconciliation of cash, cash equivalents and restricted cash: ​ ​ ​ ​ ​ ​ Cash and cash equivalents ​ $ 115,565 ​ $ 360,038 Restricted cash ​ ​ — ​ ​ 89 Total cash, cash equivalents and restricted cash ​ $ 115,565 ​ $ 360,127 ​ ​ The accompanying notes are an integral part of these condensed consolidated financial statements. ​ 11 ​ Zenas BioPharma, Inc. Notes to Condensed Consolidated Financial Statements ​ 1. Nature of Business Organization Zenas BioPharma, Inc. (“Zenas” or the “Company”) was incorporated in November 2019 as Zenas BioPharma (Cayman) Limited, an exempted company incorporated in the Cayman Islands with limited liability and commenced operations in 2020. On August 2, 2023, the Company (then known as Zenas BioPharma (Cayman) Limited) de-registered from the Cayman Islands and registered by way of continuation in the State of Delaware. Zenas is a clinical-stage global biopharmaceutical company committed to being a leader in the development and commercialization of transformative immunology-based therapies for patients in need. The Company’s goal is to build an immunology and inflammation (“I&I”) focused biopharmaceutical company. The Company has in-licensed and is developing several product candidates for the treatment of various auto-immune and rare diseases. The Company is headquartered in Waltham, Massachusetts and operates in one segment, which is the business of acquiring and developing immune-based therapies for potential commercialization. The Company’s condensed consolidated financial statements include the accounts of its wholly owned subsidiaries which include Zenas BioPharma (HK) Limited (“Zenas HK”), Zenas BioPharma (USA) LLC, Shanghai Zenas Biotechnology Co. Limited, Zenas BioPharma Securities Corp., and Zenas BioPharma GmbH. Liquidity and Capital Resources Since its inception, the Company has devoted its efforts principally to research and development and raising capital. The Company is subject to risks and uncertainties common to clinical stage companies in the biopharmaceutical industry, including, but not limited to, completing preclinical studies and clinical trials, obtaining regulatory approval for product candidates, market acceptance of products, development by competitors of new technological innovations, dependence on key personnel, the ability to attract and retain qualified employees, reliance on third-party organizations, protection of proprietary technology, compliance with government regulations, and the ability to raise additional capital to fund operations. The Company’s revenues to date have been generated from payments received under the Company’s license and collaboration agreement with Bristol-Myers Squibb Company (“BMS”), novation agreement with Tenacia Biotechnology (Hong Kong) Co., Limited (“Tenacia”), license agreement with Zai Lab (Hong Kong) Limited (“Zai”), and a royalty purchase agreement with Royalty Pharma Investments (“Royalty Pharma”) (please see Note 7, License and Collaboration Revenue and Note 9, Royalty Obligation , to these condensed consolidated financial statements). The Company has not generated any revenue from product sales since inception, and its product candidates currently under development will require significant additional research and development efforts, including extensive clinical testing and regulatory approval prior to commercialization. On September 16, 2024, the Company completed its initial public offering (“IPO”), in which the Company issued and sold 15,220,588 shares of its common stock, including 1,985,294 shares pursuant to the full exercise of the underwriters’ option to purchase additional shares, at a public offering price of $ 17.00 per share, for aggregate gross proceeds of $ 258.7 million. The Company received $ 234.3 million in net proceeds after deducting underwriting discounts, commissions and other offering expenses. In connection with the IPO, all outstanding shares of convertible preferred stock converted into 24,978,715 shares of the Company’s common stock. In connection with, and prior to, the Company’s IPO, the Company effected a 1-for- 8.6831 reverse stock split of the Company’s issued and outstanding common stock and adjusted the conversion ratio of all the Company’s outstanding convertible preferred stock. Accordingly, all share and per share amounts for all periods presented in the accompanying condensed consolidated financial statements and notes thereto have been retroactively adjusted, where applicable, to reflect the reverse stock split and the adjustment of the preferred stock conversion ratios. The Company has incurred operating losses and negative cash flows, since its inception, including net losses of $ 51.5 million and $ 38.6 million for the three months ended September 30, 2025 and 2024, respectively, and $ 137.3 million and 12 ​ $ 104.4 million for the nine months ended September 30, 2025 and 2024, respectively. As of September 30, 2025, the Company had an accumulated deficit of $ 524.7 million. Management expects operating losses and negative operating cash flows to continue for the foreseeable future. The Company expects that its existing cash, cash equivalents and investments of $ 301.6 million as of September 30, 2025, together with the $ 120.0 million of gross proceeds from the Private Investment in Public Equity (“PIPE”) received in October 2025 ( Note 16, Subsequent Events ) will be sufficient to fund its operating and capital expenditures into the fourth quarter of 2026, however it will not be sufficient to fund its operating expenses and capital expenditure requirements for at least twelve months from the date these condensed consolidated financial statements were issued. Therefore, the Company has concluded that substantial doubt exists with respect to its ability to continue as a going concern. As a result, the Company will need to raise additional capital to finance its operations. The Company’s ability to fund operations is subject to substantial risks and uncertainties. Until such time that the Company can generate significant revenue from product sales, if ever, it expects to finance its operations through a combination of private or public equity financings, debt financings or other capital sources, including collaborations with other companies or other strategic transactions and licensing agreements. The Company may be unable to raise additional funds or enter into such other agreements when needed on favorable terms or at all. If the Company is unable to obtain sufficient capital, the Company will be forced to delay, reduce or eliminate some or all of its research and development programs, product portfolio expansion or future commercialization efforts, which could adversely affect its business prospects, and the Company may be unable to continue operations. Although management continues to pursue these plans, there is no assurance that the Company will be successful in obtaining sufficient funding on terms acceptable to the Company to fund continuing operations, if at all. The accompanying condensed consolidated financial statements do not include any adjustments relating to the recoverability and classification of recorded asset amounts or the amounts and classification of liabilities that might result from the outcome of this uncertainty. Accordingly, the condensed consolidated financial statements have been prepared on a basis that assumes the Company will continue as a going concern and which contemplates the realization of assets and satisfaction of liabilities and commitments in the ordinary course of business. 2. Summary of Significant Accounting Policies The Company’s significant accounting policies are disclosed in Note 2, Summary of Significant Accounting Policies, in the audited consolidated financial statements for the year ended December 31, 2024, and notes thereto, included in the Company’s Annual Report on Form 10-K that was filed with the SEC on March 11, 2025. Since the date of those financial statements, other than disclosed herein, there have been no material changes to the Company’s significant accounting policies. Basis of Presentation and Consolidation The accompanying condensed consolidated financial statements include the operations of the Company and its wholly-owned subsidiaries. All intercompany accounts, transactions, and balances have been eliminated in consolidation. The accompanying condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) and pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”). Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”). Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been or omitted pursuant to such rules and regulations. Unaudited Interim Financial Information The accompanying unaudited condensed consolidated financial statements have been prepared on the same basis as the annual audited financial statements and in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair statement of the Company’s financial position as of September 30, 2025, and the results of operations and its cash flows for the three and nine months ended September 30, 2025 and 2024. The financial 13 ​ data and other information disclosed in these notes related to the three and nine months ended September 30, 2025 and 2024 are not necessarily indicative of the results to be expected for the year ending December 31, 2025, any other interim periods, or any future year or period. These interim financial statements should be read in conjunction with the audited financial statements as of and for the year ended December 31, 2024, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K as filed with the SEC, on March 11, 2025. ​ Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make certain estimates and assumptions that affect the reported amounts of assets, liabilities, expenses, and related disclosures. The Company bases its estimates on historical experience, known trends and other market-specific factors or other relevant factors that it believes to be reasonable under the circumstances. The Company evaluates its estimates and assumptions on an ongoing basis using such factors and adjusts those estimates and assumptions as facts and circumstances dictate. Actual results may differ from those estimates or assumptions. Significant estimates in these condensed consolidated financial statements include estimates made in connection with accrued research and development expenses, stock-based compensation, pre-initial public offering (“IPO”) valuations of common stock and the liability related to the sale of future royalties including the estimation of future payments and the related non-cash interest expense. Estimates and assumptions about future events and their effects cannot be determined with certainty and therefore require the exercise of judgement. As of the date of the issuance of these financial statements, the Company is not aware of any specific event or circumstance that would require the Company to update its estimates, assumptions and judgements or revise the carrying value of its assets or liabilities. These estimates may change as new events occur and additional information is obtained and are recognized in the financial statements as soon as they become known. Actual results could differ from those estimates and any such differences may be material to the Company’s financial statements. Royalty Obligation In September 2025, the Company and Royalty Pharma Investments 2019 ICAV (“Royalty Pharma”) entered into the Revenue Participation Right Purchase and Sale Agreement (the “Royalty Purchase Agreement”). See Note 9, Royalty Obligations, for further details of the agreement. ​ When the Company maintains significant continuing involvement in generating the underlying cash flows, royalty financings are recognized as obligations. Payments received are recorded as the principal amount of the obligation on the consolidated balance sheet as long-term liabilities. The carrying amount of the obligation is accreted to reflect the total expected royalty and related payments due to Royalty Pharma, using the effective interest method. As royalties and other related payments are made, the outstanding royalty obligation will be reduced over the estimated term of the arrangement. ​ The royalty obligation, effective interest rate, and corresponding interest expense are determined based on the Company’s estimate of future anticipated royalty payments under the arrangement. These estimates are reassessed at the end of each reporting period according to the Company’s latest projections. Should these estimated cash flows change as a result of this review, the Company will recalculate the effective interest rate and adjust the accretion of interest on the royalty obligation prospectively. Any additional funding received from Royalty Pharma will also be treated as an obligation, with a prospective adjustment to the effective interest rate applied upon receipt of such funds. ​ Recent Accounting Pronouncements In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740)—Improvements to Income Tax Disclosures (“ASU 2023-09”) , which requires a company to expand its existing income tax disclosures, specifically related to the rate reconciliation and income taxes paid. ASU 2023-09 is effective for the Company beginning in fiscal year 2025, with early adoption permitted. ASU 2023-09 may be applied retrospectively or prospectively to the financial statements. The Company is currently evaluating the impact of ASU 2023-09 on the consolidated financial statements and related disclosures. 14 ​ In November 2024, the FASB issued 2024-03, Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses (“ASU 2024-03”) , which requires entities to disclose additional information about specific expense categories in the notes to the financial statements. ASU 2024-03 is effective annual periods beginning after December 15, 2026 and for interim periods within fiscal years beginning after December 15, 2027, with early adoption permitted. ASU 2024-03 may be applied retrospectively or prospectively to the financial statements. The Company is currently evaluating the impact of ASU 2024-03 on the consolidated financial statements and related disclosures. ​ From time to time, new accounting pronouncements are issued by the “FASB” or other standard setting bodies that we adopt as of the specified effective date. Unless otherwise discussed, we do not believe that the adoption of recently issued standards have or may have a material impact on our condensed consolidated statements or disclosures. ​ 3. Fair Value Measurements The following table presents information about the Company’s assets and liabilities that are regularly measured and carried at fair value and indicate the level within the fair value hierarchy of the valuation techniques the Company utilized to determine such fair value (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of September 30, 2025 Description ​ Total Carrying Value ​ ​ Quoted Prices in Active Market (Level 1) ​ Significant Other Observable Inputs (Level 2) ​ Significant Other Observable Inputs (Level 3) Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash ​ $ 100,852 ​ $ 100,852 ​ $ — ​ $ — Money market funds ​ ​ 14,713 ​ ​ 14,713 ​ ​ — ​ ​ — Short-term investments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Commercial paper ​ ​ 6,338 ​ ​ — ​ ​ 6,338 ​ ​ — Corporate debt securities ​ ​ 38,944 ​ ​ — ​ ​ 38,944 ​ ​ — Government securities ​ ​ 130,037 ​ ​ 130,037 ​ ​ — ​ ​ — Long-term investments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Government securities ​ ​ 10,717 ​ ​ 10,717 ​ ​ — ​ ​ — Total assets ​ $ 301,601 ​ $ 256,319 ​ $ 45,282 ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, 2024 Description ​ Total Carrying Value ​ ​ Quoted Prices in Active Market (Level 1) ​ Significant Other Observable Inputs (Level 2) ​ Significant Other Observable Inputs (Level 3) Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash ​ $ 19,070 ​ $ 19,070 ​ $ — ​ $ — Money market funds ​ ​ 300,672 ​ ​ 300,672 ​ ​ — ​ ​ — Short-term investments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Commercial paper ​ ​ 3,315 ​ ​ — ​ ​ 3,315 ​ ​ — Corporate debt securities ​ ​ 8,601 ​ ​ — ​ ​ 8,601 ​ ​ — Government securities ​ ​ 19,108 ​ ​ 19,108 ​ ​ — ​ ​ — Total assets ​ $ 350,766 ​ $ 338,850 ​ $ 11,916 ​ $ — ​ There have been no material impairments of our assets measured and carried at fair value as of September 30, 2025 and December 31, 2024. In addition, there have been no changes in valuation techniques as of September 30, 2025 and 15 ​ December 31, 2024. The fair value of Level 1 instruments classified as money market funds and government securities are valued using quoted market prices in active markets. The fair value of Level 2 instruments classified as short-term investments was determined using other than quoted prices in active markets, which are either directly or indirectly observable as of the reporting date and fair value is determined using models or other valuation methodologies. During the nine months ended September 30, 2025 and year ended December 31, 2024, there were no transfers between levels. The short and long-term investments are classified as available-for-sale securities. As of September 30, 2025, the remaining contractual maturities of the available-for-sale securities were 1 to 16 months , and the balance in the Company’s accumulated other comprehensive income was comprised of activity related to the Company’s available-for-sale securities. There were no realized gains or losses recognized on the sale or maturity of available-for-sale securities during the three and nine months ended September 30, 2025 and 2024. As a result, the Company did not reclassify any amounts out of accumulated other comprehensive income for the same period. The Company had a limited number of available-for-sale securities in insignificant loss positions as of September 30, 2025, which the Company does not intend to sell and has concluded it will not be required to sell before recovery of amortized cost for the investment maturity. The following table summarizes the available-for-sale securities (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of September 30, 2025 ​ ​ Amortized Cost ​ ​ Gross Unrealized Gains ​ ​ Gross Unrealized Losses ​ ​ Fair Value Commercial paper $ 6,334 ​ $ 4 ​ $ — ​ $ 6,338 Corporate debt securities ​ 38,914 ​ ​ 31 ​ ​ ( 1 ) ​ ​ 38,944 Government securities ​ 140,680 ​ ​ 77 ​ ​ ( 3 ) ​ ​ 140,754 Total $ 185,928 ​ $ 112 ​ $ ( 4 ) ​ $ 186,036 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ As of December 31, 2024 ​ ​ Amortized Cost ​ ​ Gross Unrealized Gains ​ ​ Gross Unrealized Losses ​ ​ Fair Value Commercial paper $ 3,311 ​ $ 4 ​ $ — ​ $ 3,315 Corporate debt securities ​ 8,589 ​ ​ 12 ​ ​ — ​ ​ 8,601 Government securities ​ 19,093 ​ ​ 17 ​ ​ ( 2 ) ​ ​ 19,108 Total $ 30,993 ​ $ 33 ​ $ ( 2 ) ​ $ 31,024 ​ Certain short-term debt securities with original maturities of less than 90 days are included in cash and cash equivalents on the condensed consolidated balance sheets and are not included in the table above. ​ 4. Other Assets Other assets consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2025 December 31, 2024 Clinical trial deposits ​ $ 12,882 ​ $ 12,639 Deferred offering costs ​ ​ 837 ​ ​ — Other ​ ​ 83 ​ ​ 217 Total other assets ​ $ 13,802 ​ $ 12,856 16 ​ ​ ​ 5. Accrued Expenses Accrued expenses consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2025 December 31, 2024 External research, development and manufacturing expenses $ 34,102 ​ $ 29,338 Employee compensation and benefits ​ 8,757 ​ ​ 8,308 Professional and consultant fees ​ 1,920 ​ ​ 1,265 Income taxes payable ​ — ​ ​ 211 Other ​ 580 ​ ​ 249 Total accrued expenses $ 45,359 ​ $ 39,371 ​ ​ ​ 6 . Leases The Company has various leases for office space, which are accounted for as operating leases and generally have terms of less than two years in length, some of which have the option to renew. The Company recognizes monthly operating lease expense on a straight-line basis over the term of the lease as general and administrative expenses in the condensed consolidated statements of operations and comprehensive loss. Variable lease expense relates primarily to office lease common area maintenance, insurance, and property taxes, and it is expensed as incurred. Variable lease expense is also excluded from the calculation of lease liabilities and right-of-use-assets. The minimum lease payments under the Company’s operating leases are expected to be as follows (in thousands): ​ ​ ​ ​ Fiscal Year Amount 2025 (remaining three months) ​ $ 239 2026 ​ ​ 457 2027 ​ ​ 138 Thereafter ​ ​ — Total future minimum lease payments ​ ​ 834 Less: imputed interest ​ ​ ( 36 ) Total operating lease liabilities ​ $ 798 ​ ​ 7 . License and Collaboration Revenue License and Collaboration Agreement with Bristol-Myers Squibb In August 2023, the Company entered into a license and collaboration agreement (the “BMS Agreement”) with BMS, under which the Company granted BMS an exclusive license to (i) develop, manufacture (subject to the Company’s rights to be the exclusive manufacturer for BMS for a certain period of time), commercialize or otherwise exploit obexelimab and any biological product (irrespective of presentations, formulations or dosages) containing obexelimab but not any of the Company’s other proprietary active ingredient (the “BMS Product”) into Japan, South Korea, Taiwan, Singapore, Hong Kong and Australia (collectively, the “BMS Territory”) and (ii) develop and manufacture obexelimab and the BMS Product outside the BMS Territory provided that obexelimab and the BMS Product are solely used in the BMS Territory. Pursuant to the BMS Agreement, BMS paid the Company a one-time non-refundable upfront cash payment of $ 50.0 million. The Company is entitled to receive further separate development, regulatory milestone payments from BMS of up to approximately $ 79.5 million. The Company is also entitled to receive one-time sales milestone payments up to $ 70.0 million upon BMS achieving certain net sales milestones in a given year in the BMS Territory. The Company is also 17 ​ eligible to receive tiered high single-digit to low double-digit royalties on net sales in the BMS Territory, subject to specified reductions. The Company will continue to perform and oversee the ongoing Phase 3 trial of obexelimab in the IgG4-RD indication and BMS will participate in the performance of the study. BMS will fund their pro rata share of the total global study costs up to a specified percentage of the patients enrolled in the study from the BMS Territory. Should the percentage of patients from the BMS Territory fall below the specified percentage, BMS’s funding would proportionately decrease. The global development activities under the agreement do not represent a transaction with a customer and reimbursement payments received by the Company for global development activities are accounted for as a reduction of the related research and development expenses. As of September 30, 2025 and 2024, the Company recorded $ 1.3 million and $ 1.8 million, respectively, as a receivable included in prepaid expenses and other current assets. The Company recorded $ 1.3 million and $ 1.8 million for the three months ended September 30, 2025 and 2024, respectively, as a reduction to research and development expense for global development costs to be reimbursed by BMS. The Company recorded $ 4.2 million and $ 3.9 million for the nine months ended September 30, 2025 and 2024, respectively, as a reduction of research and development expense for global development costs to be reimbursed by BMS. The Company did no t recognize revenue related to the BMS Agreement during the three and nine months ended September 30, 2025 and 2024. Tenacia Biotechnology Co. Novation Agreement In October 2024, the Company entered into a novation agreement with Tenacia Biotechnology (Hong Kong) Co., Limited (“Tenacia”), under which the Company transferred its rights and obligations under the agreements with Dianthus to Tenacia (the “Tenacia Agreement”). Pursuant to the Tenacia Agreement, the Company, transferred all the ZB005 inventory, analytical methods and manufacturing records generated, under the Dianthus Option Agreement and License Agreement (collectively the “Dianthus Agreements”) to Tenacia, for the exclusive right to research, develop, manufacture and commercialize products within China, Hong Kong, Macau and Taiwan (“greater China”). As a result of the Tenacia Agreement, the Company has no further obligations to Dianthus pursuant to the Dianthus Agreements. Pursuant to the Tenacia Agreement, Tenacia paid the Company a one-time non-refundable upfront cash payment of $ 5.0 million, which was recognized as revenue in the fourth quarter of 2024. The Company is entitled to receive further development, regulatory and sales milestones from Tenacia of up to approximately $ 86.0 million if certain milestones are successfully achieved. The Company did not recognize revenue related to the Tenacia Agreement during the nine months ended September 30, 2025 and 2024. License Agreement with Zai Lab (Hong Kong) Limited In January 2025, the Company entered into a license agreement (the “Zai License Agreement”), with Zai, under which the Company granted Zai an exclusive sublicense to develop, manufacture and commercialize ZB001 and related programs in greater China. Under the Zai Agreement, Zai will be responsible for conducting all research and development activities, manufacturing, regulatory and commercialization in greater China. ​ Pursuant to the Zai Agreement, Zai paid the Company a one-time non-refundable upfront cash payment of $ 10.0 million. The Company is entitled to receive further development, regulatory and sales milestones from Zai up to approximately $ 117.0 million if certain milestones are successfully achieved, with passthrough obligations of $ 21.0 million due to Viridian. The Company is also eligible to receive tiered royalties on net sales in greater China, ranging from the low to mid-single digits, net of passthrough obligations due to Viridian. The Company evaluated the terms of the Zai Agreement and determined it is within the scope of ASC 606. The Company identified the following promises in the Zai Agreement that were evaluated under the scope of ASC 606: (i) transfer of the license for ZB001, (ii) licensed technology transfer (iii) licensed material transfer and (iv) continued licensed technology transfer. The Company also evaluated whether certain options outlined in the Zai Agreement represented material rights that would give rise to a performance obligation and concluded that none of the options conveyed a material right to Zai or were immaterial and, therefore, are not considered separate performance obligations within the Zai Agreement. 18 ​ The Company assessed the above promises and determined that the license for ZB001 and technology transfer are a combined distinct performance obligation within the scope of ASC 606. The licensed material transfer and the continued technology know-how transfer services are promises that are separately identifiable and considered to be distinct. The Company determined the transfer of the licensed materials and continued technology know-how transfer services were immaterial in the context of the contract based on the minimal resources required to fulfill the obligations and the estimated standalone selling price of the licensed materials. Therefore, the sublicense and technology transfer represent a single performance obligation at contract inception. The Company concluded that the transaction price of $ 10.0 million was allocated to the combined performance obligation, which was recognized upon delivery prior to March 31, 2025. The Company used the most likely amount method to estimate variable consideration and estimated that the most likely amount for each potential developmental and regulatory variable consideration milestone payment under the agreement is zero, as achievement of those milestones is uncertain and susceptible to factors outside the Company’s control. Accordingly, all such milestone payments were excluded from the transaction price. Management will reevaluate the transaction price at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur, will adjust the transaction price as necessary. Sales and royalty based milestones structured on the level of sales, were also excluded from the transaction price, as the license is deemed to be the predominant item to which the transaction price relates. The Company will recognize such milestone and royalty revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). ​ As of September 30, 2025, no milestones were achieved or deemed probable of achievement. 8. License Agreements License Agreements with Xencor, Inc. 2020 Xencor Agreement In September 2020, the Company entered into a license agreement (the “2020 Xencor Agreement”) with Xencor, Inc. (“Xencor”), under which the Company is required to pay Xencor tiered royalties on annual net sales of successfully commercialized products, including ZB002 and ZB004. The royalty percentage rates vary by geographic areas as defined in the 2020 Xencor Agreement and range from the mid-single digits to mid-teens. The Company is also obligated to reimburse Xencor for third-party costs incurred for certain patent filings, prosecution and maintenance as further specified in the 2020 Xencor Agreement. During the nine months ended September 30, 2025 and 2024, the Company incurred no such reimbursable costs. 2021 Xencor Agreement In May 2021, the Company entered into a license agreement with Xencor (the “2021 Xencor Agreement”), under which the Company obtained an exclusive, royalty-bearing, sublicensable worldwide license to research, develop, manufacture, market and sell obexelimab. The Company is also obligated to make regulatory milestone payments up to $ 75.0 million and one-time sales milestone payments up to $ 385.0 million upon achieving milestone events of net sales in a given calendar year in the territory equal to certain threshold amounts. In addition, the Company is required to pay Xencor tiered royalties on annual net sales of successfully commercialized products utilizing obexelimab, with the royalty percentages varying based on regions and ranging from the mid-single digits to the mid-teens. For the nine months ended September 30, 2025 and 2024, the Company recorded no reimbursable patent-related costs. License Agreement with Viridian Therapeutics, Inc. In October 2020, the Company entered into a license agreement with Viridian Therapeutics, Inc. (the “Viridian Agreement”) to obtain an exclusive, royalty-bearing, sublicensable license to research, develop, manufacture, market and sell certain antibody product candidates based on Viridian’s proprietary technology. The Company’s license rights are limited to non-oncology indications and are limited to China, Hong Kong, Macau and Taiwan (“Zenas Territories”). Viridian retains its rights to develop and commercialize such product candidates outside of the Zenas Territories. In 19 ​ December 2021, the Company and Viridian entered into two letter agreements to authorize initiation of certain manufacturing and development activities related to the licensed product candidate, ZB001. Under the terms of the letter agreements, Viridian engaged a third-party contract manufacturer to initiate certain work related to ZB001. In May 2022, the Company entered into a manufacturing development and supply agreement (“Viridian Supply Agreement”). In January 2025, the Company entered into a third amendment to the Viridian Agreement, under which the Company is obligated to make development and sales milestone payments to Viridian, totaling $ 21.0 million, based on achievement of certain specified development and sales milestones, and royalties on net sales. ​ In January 2025, the Company entered the Zai License Agreement under which the Company granted Zai an exclusive sublicense to develop, manufacture and commercialize ZB001 and related programs in greater China. In connection with the Zai License Agreement, the Company assigned the Viridian Supply Agreement to Zai. For additional information on the Zai Agreement, please see License Agreement with Zai Lab (Hong Kong) Limited in Note 7 – License and Collaboration Revenue to these condensed consolidated financial statements. ​ During the three and nine months ended September 30, 2025, the Company recognized no expense related to Viridian contract manufacturing organization (“CMO”) costs. During the three and nine months ended September 30, 2024, the Company recognized no expense and $ 0.1 million in expense related to Viridian CMO costs, respectively. Viridian has agreed to reimburse the Company for certain services the Company performs on Viridian’s behalf, with reimbursements being recorded as a reduction in research and development expenses. During the three and nine months ended September 30, 2025, the Company recorded an immaterial amount and $ 0.2 million in reimbursable expenses, respectively. During the three and nine months ended September 30, 2024, the Company recorded $ 0.5 million and $ 1.5 million in reimbursable expenses, respectively. Additionally, during the nine months ended September 30, 2025 and 2024, no milestones were achieved. 9. Royalty Obligation In September 2025, the Company and Royalty Pharma entered into the Royalty Purchase Agreement. Pursuant to the Royalty Purchase Agreement, the Company received a $ 75.0 million upfront payment in exchange for which Royalty Pharma purchased the right to receive, for each calendar quarter, (i) 5.5 % of net sales of obexelimab products sold by the Company and its affiliates worldwide, (ii) 5.5 % of net sales of obexelimab products sold by licensees of Zenas and its affiliates in the U.S., the United Kingdom and the European Union, (iii) 25 % of royalty income payable to Zenas or any of its affiliates on sales of obexelimab products in countries other than the U.S., the United Kingdom, and in the European Union by its licensees pursuant to out-licenses less royalty payments payable by Zenas to Xencor Inc. and (iv) 25 % of non-royalty income attributable to obexelimab products payable to Zenas or any of its affiliates by its licensees (other than certain milestone payments payable by Bristol-Myers Squibb) pursuant to out-licenses and allocated to countries other than the U.S., the United Kingdom and in the European Union. The Royalty Purchase Agreement provides for an additional $ 225.0 million of payments to be paid to the Company by Royalty Pharma upon the occurrence of certain triggering events which includes (1) $ 75.0 million payable upon the achievement of certain milestones with respect to Zenas’ INDIGO Phase 3 Trial of obexelimab for the treatment of patients with IgG4-Related Disease on or before a specified date, (2) $ 75.0 million payable following receipt of marketing approval for obexelimab from the U.S. Food and Drug Administration (the “FDA”) for the treatment of IgG4-Related Disease on or before a specified date and (3) $ 75.0 million payable following receipt of marketing approval for obexelimab from the FDA for the treatment of systemic lupus erythematosus on or before a specified date. ​ The Company accounted for the Royalty Purchase Agreement as a debt financing, primarily because it has significant continuing involvement in generating the future revenue on which the royalty payments are based. The $ 75.0 million upfront payment received was recorded as a liability, net of issuance costs of $ 3.7 million. The effective interest rate was determined based on the Company’s projections of future royalty payments. The Company will evaluate the estimated timing and amount of future royalty payments for each reporting period and will revise the effective interest rate prospectively if those estimates change materially. ​ The fair value of the liability approximates the carrying value and was determined based on the current estimate of the timing and amount of expected future royalty payments expected to be paid over the estimated term of the Royalty 20 ​ Purchase Agreement, which are subject to significant estimation uncertainty and are based on various assumptions made by the Company. These assumption inputs are determined to be Level 3 inputs in the fair value hierarchy as they involve significant unobservable inputs and judgment. ​ The following table shows the activity for the royalty obligation during the three and nine months ended September 30, 2025 (in thousands): ​ ​ ​ ​ ​ ​ Amount Proceeds from royalty obligation ​ $ 75,000 Issuance costs ​ ​ ( 3,690 ) Interest expense related to royalty obligation ​ ​ 1,679 Royalty obligation as of September 30, 2025 ​ $ 72,989 Effective interest rate ​ ​ 30.7 % ​ ​ ​ ​ 10. Common Stock In September 2024, upon the completion of the IPO, the Company restated its certificate of incorporation, pursuant to which the Company is authorized to issue 175,000,000 shares of common stock $ 0.0001 par value. The voting, dividend and liquidation rights of the holders of the Company’s common stock were subject to and qualified by the rights, powers and preference of the holders of any preferred stock then issued and outstanding. The holders of the common stock are entitled to one vote for each share of common stock held at all meetings of stockholders (and written actions in lieu of meetings), and there are no cumulative voting rights. The Company had reserved the following shares of common stock for the potential conversion of outstanding stock options: ​ ​ ​ ​ ​ ​ ​ September 30, 2025 December 31, 2024 Options to purchase common stock ​ 10,507,497 ​ 8,706,197 Remaining shares reserved for future issuance ​ 507,134 ​ 359,399 RSUs ​ 525,350 ​ — Employee stock purchase plan ​ 773,122 ​ 397,956 Total ​ 12,313,103 ​ 9,463,552 ​ ​ 11. Stock-Based Compensation 2024 Plan On September 3, 2024, the Board of Directors (the “Board”) adopted the 2024 Equity Incentive Plan (the “2024 Plan”), which became effective immediately prior to the effectiveness of the registration statement for the Company’s IPO. The 2024 Plan provides for the award of incentive stock options, nonstatutory stock options, stock appreciation rights, restricted stock awards, unrestricted stock, restricted stock units and other stock-based awards. The number of shares reserved and available for issuance under the 2024 Plan will automatically increase each January 1, beginning on January 1, 2025 through January 1, 2034, by the number of shares equal to the lesser of (i) five percent of the aggregate number of shares of common stock outstanding as of such date, and (ii) a number of shares as may be determined by the Board on or prior to such date. In January 2025, the number of shares of common stock available for issuance under the Company’s 2024 Plan, was increased by 2,089,670 shares of common stock due to the automatic annual provision to increase shares of common stock available under the 2024 Plan. As of September 30, 2025, 507,134 shares of common stock were available for issuance under the 2024 Plan. 21 ​ Stock Options The Company has granted stock-based awards with either service or performance based vesting conditions. Compensation expense related to awards to employees and directors with service based vesting conditions is recognized on a straight-line basis based on the grant date fair value over the associated service period of the award, which is generally the vesting term. Compensation expense related to awards to employees with performance based vesting conditions is recognized based on the grant date fair value once the achievement of the performance condition is probable. From time to time, the Company grants equity awards to newly hired employees as an inducement to enter into employment with the Company. The grants constitute "employment inducement grants" in accordance with Rule 5635(c)(4) of the Nasdaq Listing Rules and are issued outside of the 2024 Plan. The inducement grants include non-statutory stock options to purchase shares of the Company's common stock. The inducement grants have terms and conditions consistent with those set forth under the 2024 Plan and vest under the same respective vesting schedules as stock option awards granted under the 2024 Plan. The inducement grants are included in the stock option award tables below. As of September 30, 2025, the Company granted 762,000 non-statutory stock options as inducement grants. No inducement grants were awarded during 2024. ​ The following table presents a summary of the Company’s stock option activity and related information: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Number of Shares Weighted - Average Exercise Price Weighted-Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding - December 31, 2024 ​ 8,706,197 ​ $ 13.21 ​ ​ ​ $ 2,104 Granted ​ 2,703,600 ​ $ 10.82 ​ ​ ​ ​ ​ Exercised ​ ( 377,285 ) ​ $ 6.59 ​ ​ ​ $ 1,731 Forfeited or cancelled ​ ( 525,015 ) ​ $ 12.59 ​ ​ ​ ​ ​ Outstanding - September 30, 2025 ​ 10,507,497 ​ $ 12.86 ​ 8.81 ​ $ 98,133 Options vested and exercisable as of September 30, 2025 ​ 2,833,037 ​ $ 12.12 ​ 8.12 ​ $ 28,548 Options vested and expected to vest as of September 30, 2025 ​ 10,507,497 ​ $ 12.86 ​ 8.81 ​ $ 98,133 ​ The aggregate intrinsic value of the stock options is calculated as the difference between the exercise price of the options and the fair value of the Company’s common stock for those stock options that had an exercise price lower than the fair value of the Company’s common stock as of the measurement date of September 30, 2025. Restricted Stock Units The Company granted to certain employees restricted stock units (“RSUs”) that are subject to time-based vesting conditions, that vest equally over four years , assuming continued employment. RSUs with time-based vesting conditions are valued on the grant date using the grant date market value price of the underlying shares of the Company’s common stock. The Company did not grant any RSU’s in 2024. The following table summarizes the Company’s RSU activity: ​ ​ ​ ​ ​ ​ ​ ​ Number of Shares ​ Weighted - Average Grant Date Fair Value Unvested as of December 31, 2024 ​ — ​ $ — Granted ​ 538,550 ​ $ 12.15 Vested ​ — ​ $ — Forfeited ​ ( 13,200 ) ​ $ 11.94 Unvested as of September 30, 2025 ​ 525,350 ​ $ 12.16 ​ 22 ​ No RSUs vested during the current or prior year periods. As of September 30, 2025, there was $ 81.2 million of unrecognized stock-based compensation related to unvested stock options, granted RSU’s and the Employee Stock Purchase Plan (the “ESPP”), which is expected to be recognized over a weighted-average period of 3.0 years. The Company recognized stock-based compensation expense related to the issuance of equity awards to employees and directors in the condensed consolidated statement of operations as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended September 30, ​ ​ Nine Months Ended September 30, ​ ​ ​ 2025 ​ ​ 2024 ​ ​ 2025 ​ ​ 2024 Research and development ​ $ 2,403 ​ $ 1,257 ​ $ 6,097 ​ $ 2,378 General and administrative ​ ​ 4,933 ​ ​ 1,586 ​ ​ 12,670 ​ ​ 2,948 Total stock-based compensation expense ​ $ 7,336 ​ $ 2,843 ​ $ 18,767 ​ $ 5,326 ​ Employee Stock Purchase Plan On September 3, 2024, the Board adopted the 2024 Employee Stock Purchase Plan (the “ESPP”), which became effective immediately prior to the effectiveness of the registration statement for the Company’s IPO. The number of shares of common stock available under the ESPP will automatically increase on January 1st of each year, beginning on January 1, 2025 through January 1, 2034, by the number of shares equal to the lesser of (i) one percent of the aggregate number of shares of common stock outstanding as of such date, and (ii) a number of shares as may be determined by the Board on or prior to such date, up to a maximum of 1,000,000 shares in the aggregate per year. On January 1, 2025, the number of shares of common stock authorized for issuance under the ESPP increased automatically by 417,934 shares and as of September 30, 2025, a total of 773,122 shares were available for future issuance under the ESPP. During the three and nine months ended September 30, 2025, there were 42,768 shares issued under the ESPP. ​ ​ 12. Net Loss Per Share The Company’s potentially dilutive securities, which include convertible preferred stock, restricted stock and stock options, have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share. Therefore, the weighted-average number of common shares outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders is the same. The Company excluded the following shares from the computation of diluted net loss per share attributable to common stockholders as of September 30, 2025 and 2024 because including them would have had an anti-dilutive effect: ​ ​ ​ ​ ​ ​ ​ ​ September 30, ​ ​ 2025 ​ 2024 Unvested restricted stock units ​ 525,350 ​ — Options to purchase common stock ​ 10,507,497 ​ 8,630,075 ​ ​ ​ ​ 13. Commitments and Contingencies Operating Leases The Company has entered into arrangements for leases of office space; see Note 6, Leases , for details. License Agreements The Company entered into license agreements under which it is obligated to make fixed and contingent payments; see Note 8, License Agreements , for details. 23 ​ Royalty Obligation The Company entered into a royalty purchase agreement under which it is obligated to make contingent payments related to future net sales and royalty income of obexelimab; see Note 9, Royalty Obligation for details. Other Contracts The Company has entered into agreements with certain vendors for the provision of services that the Company is not contractually able to terminate for convenience and thereby avoid any and all future obligations to the vendors. Under such agreements, the Company is contractually obligated to make certain minimum payments to the vendors, with the exact amounts in the event of termination to be based on the timing of the termination and the exact terms of the agreement. As of September 30, 2025, our total non-cancellable clinical manufacturing contract payment obligations are $ 18.7 million of which the full obligation is payable within 12 months. Indemnification Agreements In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its board of directors and certain officers that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or services as directors. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. To date, the Company has not incurred any material costs as a result of such indemnifications. The Company is not currently aware of any indemnification claims and had not accrued any liabilities related to such obligations in its condensed consolidated financial statements as of September 30, 2025. Litigation and Other Proceedings The Company may periodically become subject to legal proceedings and claims arising in the ordinary course of business. As of September 30, 2025, the Company was not subject to any material legal proceedings which would reasonably be expected to have a material adverse effect on the Company’s financial results. ​ 14. Related Party Transactions Xencor, Inc. The Company has obtained exclusive, worldwide licenses from Xencor to research, develop, manufacture, market and sell three antibody product candidates pursuant to two license agreements. The Company has concluded that Xencor is a related party, due to the issuance of convertible preferred stock in December 2020 and April 2023. In connection with the completion of the IPO, in September 2024, all outstanding shares of preferred stock converted into shares of common stock. As of September 30, 2025, Xencor held less than 10 % of shares of the Company’s outstanding common stock. Viridian Therapeutics, Inc. The Company has obtained a license from Viridian to research, develop, manufacture, market and sell an antibody product candidate in China. The Company has concluded that Viridian is a related party because although Fairmount Funds Management LLC owns less than 10 % of shares of the Company’s outstanding common stock, they have a seat on the Board and are also a 10% or greater stockholder of Viridian and have two seats on Viridian’s board of directors. As initial consideration for this license, the Company issued 38,707 shares of its common stock to Viridian during the year ended December 31, 2020. As of September 30, 2025, Viridian held 0.1 % of shares of the Company’s outstanding common stock. Zai Lab (Hong Kong) Limited 24 ​ The Company has granted a sublicense to Zai to develop, manufacture and commercialize ZB001 and related programs in greater China. The Company has concluded that Zai is a related party, as the Company’s CEO and Chairman is a member of Zai’s board of directors. For additional information on these arrangements, please see Note 7, License and Collaboration Revenue and Note 8, License Agreements, to these condensed consolidated financial statements. 15. Segment Information The Company manages its operations on a consolidated basis as a single reportable segment focused on the research and development of precision immunology-based therapies. The accounting policies of the single reportable segment are identical to those described in Note 2, Summary of Significant Accounting Policies . When evaluating the Company’s financial performance, the Company’s chief operating decision-maker (the “CODM”), its Chief Executive Officer regularly reviews consolidated net loss, total expense and direct expenses by program and compared to budget. The CODM allocates resources based on the Company’s available cash resources, and forecasted expenditures on a consolidated basis, as well as an assessment of the probability of success of its research and development activities on a program basis. Segment asset information regularly provided to the CODM is consistent with that reported on the consolidated balance sheets with particular emphasis on the Company’s available liquidity, including its cash, cash equivalents and investment balances. Revenue is primarily attributed to individual countries based on the entity owning the license. During the three months ended September 30, 2025, the Company did no t recognize revenue and for nine months ended September 30, 2025, $ 10.0 million was recognized as revenue which was attributed to Zenas HK. The Company did no t recognize revenue during the three or nine months ended September 30, 2024. The following table presents certain financial data for the Company’s reportable segment for the three and nine months ended September 30, 2025 and 2024 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ For the three months ended September 30, ​ ​ For the nine months ended September 30, ​ ​ ​ 2025 ​ ​ 2024 ​ ​ 2025 ​ ​ 2024 Revenue ​ $ — ​ $ — ​ $ 10,000 ​ $ — Less: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Direct research and development expenses: 1 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Obexelimab ​ ​ 20,753 ​ ​ 21,326 ​ ​ 74,006 ​ ​ 56,408 Other programs (ZB002 & ZB004) ​ ​ 467 ​ ​ 384 ​ ​ 1,204 ​ ​ 1,850 Partnered regional programs (ZB001 & ZB005) ​ ​ 172 ​ ​ 2,344 ​ ​ 134 ​ ​ 6,367 Unallocated research and development 2 ​ ​ 10,607 ​ ​ 8,219 ​ ​ 30,902 ​ ​ 22,979 General and administrative 3 ​ ​ 8,245 ​ ​ 5,868 ​ ​ 25,060 ​ ​ 15,335 Acquired in-process research and development ​ ​ 5,000 ​ ​ — ​ ​ 5,000 ​ ​ — Stock-based compensation ​ ​ 7,336 ​ ​ 2,843 ​ ​ 18,767 ​ ​ 5,326 Other segment items 4 ​ ​ ( 1,081 ) ​ ​ ( 2,378 ) ​ ​ ( 7,778 ) ​ ​ ( 3,881 ) Segment net loss ​ $ ( 51,499 ) ​ $ ( 38,606 ) ​ $ ( 137,295 ) ​ $ ( 104,384 ) ​ 1 Direct research and development expenses primarily consist of direct costs incurred to specific program research and development activities, including costs to conduct clinical trials and to manufacture clinical drug supply. 2 Unallocated research and development expenses primarily consist of indirect costs incurred in support of overall research and development activities and non-specific programs, including activities that benefit multiple programs, such as personnel costs for employees involved in research and development activities, excluding stock-based compensation, as well as contract services not allocated to specific programs. 3 General and administrative expenses primarily consist of professional fees, depreciation expense, facilities expenses as well as all other personnel costs, excluding stock-based compensation. 4 Other segment items consist of other income (expense), net, and income tax benefit (provision). Other income (expense), net consists of interest income, interest expense related to the royalty obligation and realized and unrealized gains and losses on foreign currency transactions . 25 ​ 16. Subsequent Events License Agreement with InnoCare Pharma Inc. In October 2025, the Company entered into a License Agreement (the “InnoCare License Agreement”) with InnoCare Pharma Inc. (“InnoCare”). Under the InnoCare License Agreement, InnoCare granted the Company exclusive rights to develop, manufacture, and commercialize: i) orelabrutinib, in the multiple sclerosis (“MS”) field worldwide, and in all non-oncology indications outside Greater China and Brunei, Burma, Cambodia, Timor-Leste, Indonesia, Laos, Malaysia, Philippines, Singapore, Thailand and Vietnam (“Southeast Asia”), ii) ZB021 (an IL-17AA/AF inhibitor) in all fields of use worldwide, excluding Greater China and Southeast Asia and iii) ZB022 (a TYK2 inhibitor) in all fields of use worldwide. The Company also obtained certain non-exclusive rights to perform development and manufacturing activities in Greater China and Southeast Asia to support each program in its respective licensed territories. Pursuant to the InnoCare License Agreement, the Company agreed to make a one-time non-refundable upfront cash payment of $ 35.0 million, $ 5.0 million of which was paid as of September 30, 2025, prior to the transaction closing and was recorded in the condensed consolidated statement of operations and comprehensive loss as acquired in-process research and development. The Company also agreed to issue upfront, 5,000,000 shares of common stock to InnoCare in a private placement in exchange for these rights. The Company is also required to make an additional one-time non-refundable cash payment of $ 25.0 million and issue an additional 2,000,000 shares of common stock through a private placement upon the occurrence of Zenas’ initiated Phase 3 clinical trial for orelabrutinib in any indication other than primary progressive MS, or by March 31, 2026, upon the occurrence of certain specified events, whichever comes first. In addition, the Company has agreed to make one-time, potential near-term milestone payments of $ 20 million each, upon the achievement of certain regulatory milestones for ZB021 and ZB022 (the “Regulatory Milestones”). The Company is further obligated to pay future regulatory and commercial milestones of up to $ 723.0 million related to orelabrutinib, and future development, regulatory, and commercial milestones of up to $ 656.0 million, inclusive of the two $ 20.0 million Regulatory Milestones specified above, for each preclinical compound if certain milestones are successfully achieved. In addition, the Company may be obligated to pay royalties on net sales at rates ranging from high-single digits to high-teens for orelabrutinib, and mid-single digits to mid-teens for the preclinical compounds. The Company is obligated to reimburse InnoCare approximately $ 4.0 million, for certain costs related to the acquired programs which were incurred prior to and after the effective date of the InnoCare License Agreement, including clinical trial startup costs and Investigational New Drug (“IND”) enabling activities. The Company simultaneously entered into a Subscription Agreement and Registration Rights Agreement with InnoCare related to the shares of common stock issued and to be issued in the private placement. The Subscription Agreement provides transfer restrictions on the InnoCare shares and other customary representations, warranties and covenants that were made solely for the benefit of the parties to the Securities Purchase Agreement. PIPE In October 2025, the Company entered into a Securities Purchase Agreement and Registration Rights Agreement related to the PIPE transaction, pursuant to which the Company sold (i) 6,262,112 shares of common stock to certain institutional and accredited investors at a price of $ 19.00 per share and (ii) 48,918 shares of common stock to certain directors and officers of the Company at a price of $ 20.85 per share for gross proceeds of approximately $ 120.0 million, before deducting placement agent fees and other offering expenses. At- the-Market (“ATM”) Program In October 2025, the Company filed a registration statement on Form S-3 (the “Registration Statement”) with the SEC, which registered the offering, issuance and sale of common stock, preferred stock, warrants and debt securities, or any combination thereof, in an amount and on terms that the Company will determine at the time of the respective offering. The Company simultaneously entered into a sales agreement with Jefferies LLC as sales agent to provide for the issuance and sale by the Company of up to $ 200.0 million of common stock from time to time in ATM offerings under the Registration Statement. ​ 26 ​