SCHEDULE 13G 0001758866 XXXXXXXX LIVE Common Stock, par value $0.01 per share 02/13/2024 0001274792 MERRIMACK PHARMACEUTICALS INC 590328209 ONE BROADWAY 14TH FLOOR CAMBRIDGE MA 02142 Rule 13d-1(c) ADAR1 Partners, LP DE 0.00 902350.00 0.00 902350.00 902350.00 6.3 PN ADAR1 Capital Management, LLC TX 0.00 902350.00 0.00 902350.00 902350.00 6.3 OO ADAR1 Capital Management, LLC acts as an investment adviser to, and manages investment and trading accounts of, ADAR1 Partners, LP. ADAR1 Capital Management, LLC may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP. ADAR1 Capital Management GP, LLC TX 0.00 902350.00 0.00 902350.00 902350.00 6.3 OO ADAR1 Capital Management GP, LLC acts as the general partner of ADAR1 Partners, LP. ADAR1 Capital Management GP, LLC may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP. Daniel Schneeberger V8 0.00 902350.00 0.00 902350.00 902350.00 6.3 IN ADAR1 Capital Management, LLC acts as an investment adviser to, and manages investment and trading accounts of, ADAR1 Partners, LP. ADAR1 Capital Management GP, LLC acts as the general partner of ADAR1 Partners, LP. Mr. Schneeberger is the Manager of ADAR1 Capital Management, LLC and ADAR1 Capital Management GP, LLC. Mr. Schneeberger may be deemed to indirectly beneficially own securities held by ADAR1 Partners, LP. MERRIMACK PHARMACEUTICALS INC ONE BROADWAY, 14TH FLOOR, CAMBRIDGE, MASSACHUSETTS, 02142 This Schedule is being filed on behalf of each of the following persons (each, a "Reporting Person" and collectively, the "Reporting Persons") i) ADAR1 Partners, LP ("ADAR1 Fund"); ii) ADAR1 Capital Management, LLC ("ADAR1 Capital Management"); iii) ADAR1 Capital Management GP, LLC ("ADAR1 General Partner"); and iv) Daniel Schneeberger ("Mr. Schneeberger") This Schedule relates to shares of common stock of the Issuer, par value $0.01 per share ("Shares"), directly held by ADAR1 Fund. ADAR1 Capital Management acts as an investment adviser to, and manages investment and trading accounts of, ADAR1 Fund. ADAR1 General Partner acts as the general partner of ADAR1 Fund. ADAR1 Capital Management and ADAR1 General Partner may be deemed to indirectly beneficially own securities held by ADAR1 Fund. Mr. Schneeberger is the Manager of ADAR1 Capital Management and ADAR1 General Partner. Mr. Schneeberger may be deemed to indirectly beneficially own securities held by ADAR1 Fund. Each Reporting Person declares that neither the filing of this Schedule nor anything herein shall be construed as an admission that such person is, for the purposes of Section 13(d) or 13(g) of the Act or any other purpose, (i) acting (or has agreed or is agreeing to act) with any other person as a partnership, limited partnership, syndicate, or other group for the purpose of acquiring, holding, or disposing of securities of the Issuer or otherwise with respect to the Issuer or any securities of the Issuer or (ii) a member of any syndicate or group with respect to the Issuer or any securities of the Issuer. The address of the principal business office of each of the Reporting Persons is 3503 Wild Cherry Drive, Building 9, Austin, Texas 78738. i) ADAR1 Fund is a Delaware limited partnership; ii) ADAR1 Capital Management is a Texas limited liability company; iii) ADAR1 General Partner is a Texas limited liability company; and iv) Mr. Schneeberger is a citizen of Switzerland. Y As of the date hereof, each of the Reporting Persons may be deemed to be the beneficial owner of 902,350 Shares. As of the date hereof, each of the Reporting Persons may be deemed to be the beneficial owner of approximately 6.30% of the Shares outstanding, based on 14,320,953 Shares outstanding as of October 31, 2023, as reported in the Issuer's Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission on November 2, 2023. 0 902,350 0 902,350 Y N Y Y Y Y N By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11. ADAR1 Partners, LP Daniel Schneeberger 02/22/2024 ADAR1 Capital Management, LLC Daniel Schneeberger 02/22/2024 ADAR1 Capital Management GP, LLC Daniel Schneeberger 02/22/2024 Daniel Schneeberger Daniel Schneeberger 02/22/2024 EXHIBIT_A.txt EX-1 Joint Filing Agreement RVhISUJJVCBBDQoNCiAgICAgIEpPSU5UIEZJTElORyBBR1JFRU1FTlQNCg0KVGhlIHVuZGVy c2lnbmVkIGhlcmVieSBhZ3JlZSB0aGF0IHRoZSBzdGF0ZW1lbnQgb24gU2NoZWR1bGUgMTNH IHdpdGggcmVzcGVjdA0KdG8gdGhlIHNoYXJlcyBvZiBjb21tb24gc3RvY2ssIHBhciB2YWx1 ZSAkMC4wMSBwZXIgc2hhcmUsIG9mDQpNZXJyaW1hY2sgUGhhcm1hY2V1dGljYWxzLCBJbmMu IGRhdGVkIGFzIG9mIEZlYnJ1YXJ5IDIyLCAyMDI0IGlzLCBhbmQgDQphbnkgYW1lbmRtZW50 cyB0aGVyZXRvIHNpZ25lZCBieSBlYWNoIG9mIHRoZSB1bmRlcnNpZ25lZCBzaGFsbCBiZSwg ZmlsZWQNCm9uIGJlaGFsZiBvZiBlYWNoIG9mIHVzIHB1cnN1YW50IHRvIGFuZCBpbiBhY2Nv cmRhbmNlIHdpdGggdGhlIHByb3Zpc2lvbnMNCm9mIFJ1bGUgMTNkLTEoaykgdW5kZXIgdGhl IFNlY3VyaXRpZXMgRXhjaGFuZ2UgQWN0IG9mIDE5MzQsIGFzIGFtZW5kZWQuDQoNCkFEQVIx IFBBUlRORVJTLCBMUA0KL3MvIERhbmllbCBTY2huZWViZXJnZXINCk1hbmFnZXIgb2YgQURB UjEgQ2FwaXRhbCBNYW5hZ2VtZW50IEdQLCBMTEMsIHRoZSBHZW5lcmFsIFBhcnRuZXIgb2YN CkFEQVIxIFBhcnRuZXJzLCBMUA0KDQpBREFSMSBDQVBJVEFMIE1BTkFHRU1FTlQsIExMQw0K L3MvIERhbmllbCBTY2huZWViZXJnZXINCk1hbmFnZXIgb2YgQURBUjEgQ2FwaXRhbCBNYW5h Z2VtZW50LCBMTEMNCg0KQURBUjEgQ0FQSVRBTCBNQU5BR0VNRU5UIEdQLCBMTEMNCi9zLyBE YW5pZWwgU2NobmVlYmVyZ2VyDQpNYW5hZ2VyIG9mIEFEQVIxIENhcGl0YWwgTWFuYWdlbWVu dCBHUCwgTExDDQoNCkRBTklFTCBTQ0hORUVCRVJHRVINCi9zLyBEYW5pZWwgU2NobmVlYmVy Z2VyDQo=