MacroGenics Provides Phase 2 TAMARACK Study Early Interim Safety Data and Plans for Future Disclosures

• Early interim safety data from Phase 2 TAMARACK study, including comparison to retrospective analysis from Phase 1 study, as submitted in ASCO abstract
• Company plans to provide updated interim data, including safety and preliminary efficacy, by May 31
• Company plans to provide additional clinical data – including rPFS – in the Fall of 2024

ROCKVILLE, MD, April 03, 2024 (GLOBE NEWSWIRE) --  MacroGenics, Inc. (NASDAQ: MGNX), a biopharmaceutical company focused on discovering, developing, manufacturing and commercializing innovative antibody-based therapeutics for the treatment of cancer, today provided an update on the Phase 2 TAMARACK study of vobramitamab duocarmazine (vobra duo, previously known as MGC018) in patients with metastatic castration-resistant prostate cancer (mCRPC).

As previously disclosed, safety data from the Company’s ongoing TAMARACK Phase 2 study was submitted in early February to the American Society of Clinical Oncology (ASCO) for presentation at the upcoming Annual Meeting that begins May 31. The abstract containing this early interim data, based on a January 4, 2024 data cut-off, was not accepted. The submitted abstract is provided below.

“While the TAMARACK data will not be presented at the ASCO Annual Meeting, we intend to maintain our previously disclosed plan to share further TAMARACK interim data, including updated safety and preliminary efficacy, by the end of May,” said Scott Koenig, M.D., Ph.D., President and Chief Executive Officer. “This updated information will be based upon a future data cut-off. In addition, we still anticipate presenting updated clinical data – including radiographic progression-free survival, or rPFS, the study’s primary endpoint – in the Fall of 2024.”

Abstract as submitted on February 6, 2024:

“Title
Vobramitamab duocarmazine (vobra duo), a B7-H3 directed antibody drug conjugate (ADC) in metastatic castration resistant prostate cancer (mCRPC): Early data from the Phase 2 TAMARACK study.

Background
Vobra duo (MGC018) is an ADC with a duocarmycin-based DNA-alkylating payload. Vobra duo targets B7-H3, which is highly expressed in multiple tumor types including prostate cancer and has limited expression in normal tissue. Phase 1 testing (NCT03729596) of vobra duo at 3.0 mg/kg Q3W demonstrated anti-tumor activity in mCRPC, although adverse events resulted in high rates of dose modifications and early treatment discontinuation. Lowering the starting dose may improve tolerability, extend treatment duration, and enhance effectiveness.