8-K: MacroGenics Provides Update on Phase 2 TAMARACK Study, Plans for Future Data Releases

MacroGenics announced early interim safety data from its Phase 2 TAMARACK study of vobramitamab duocarmazine, with plans to release further data in the coming months.

Summary

• MacroGenics has provided an update on its Phase 2 TAMARACK study, which is evaluating vobramitamab duocarmazine (vobra duo) for metastatic castration-resistant prostate cancer (mCRPC).
• The company submitted early interim safety data to the American Society of Clinical Oncology (ASCO), but the abstract was not accepted for presentation at the upcoming annual meeting.
• Despite this, MacroGenics plans to share updated interim data, including safety and preliminary efficacy, by the end of May.
• The company also anticipates presenting updated clinical data, including radiographic progression-free survival (rPFS), in the Fall of 2024.
• The TAMARACK study is assessing two dose levels of vobra duo (2.0 mg/kg and 2.7 mg/kg) administered every four weeks.
• The study enrolled 182 patients with mCRPC, with 177 receiving vobra duo.
• At the January 4, 2024 data cut-off, patients had received a median of 3 cycles of vobra duo, with 156 patients still on treatment.
• Preliminary safety data suggests that reducing the dose and frequency of vobra duo improves its safety and tolerability compared to the Phase 1 study.
• The most common treatment-emergent adverse events (TEAEs) included asthenia, nausea, fatigue, and decreased appetite.

Sentiment

Score: 7

Explanation: The document presents a positive outlook with improved safety data compared to the Phase 1 study, but the lack of ASCO presentation and the presence of adverse events temper the overall sentiment. The planned future data releases are also a positive sign.

Positives

• Preliminary safety data suggests that reducing the dose and frequency of vobra duo improves its safety and tolerability in men with mCRPC.
• The rate of drug interruption and discontinuation due to adverse events in the TAMARACK study appears to be lower than in the Phase 1 study.
• The Independent Data Monitoring Committee (IDMC) recommended continuing the study as planned without modification.
• The study is ongoing with 156 patients still receiving treatment.

Negatives

• The abstract containing early interim data was not accepted for presentation at the ASCO Annual Meeting.
• Treatment-emergent adverse events (TEAEs) were common, with asthenia, nausea, and fatigue being the most frequent.
• A significant percentage of patients experienced treatment-emergent adverse events (TEAEs) of grade 3 or higher (25.3% in the 2.0 mg/kg group and 31.4% in the 2.7 mg/kg group).

Risks

• The study is still ongoing, and the final results may differ from the preliminary data.
• The safety and efficacy of vobra duo need to be further evaluated in the ongoing study.
• There is a risk that the updated data may not be positive or may not meet the study's primary endpoint.
• The company's future plans are subject to various risks and uncertainties, including regulatory approvals and market acceptance.

Future Outlook

MacroGenics plans to release updated interim data, including safety and preliminary efficacy, by the end of May and updated clinical data, including radiographic progression-free survival (rPFS), in the Fall of 2024.

Management Comments

• Scott Koenig, M.D., Ph.D., President and Chief Executive Officer, stated that the company intends to maintain its previously disclosed plan to share further TAMARACK interim data by the end of May.
• He also mentioned that the company anticipates presenting updated clinical data in the Fall of 2024.

Industry Context

The development of antibody-drug conjugates (ADCs) like vobramitamab duocarmazine is a growing area of focus in cancer treatment, particularly for solid tumors like prostate cancer. The results of this study will be closely watched by the oncology community and competitors in the ADC space.

Comparison to Industry Standards

• The Phase 1 study of vobra duo at 3.0 mg/kg Q3W resulted in high rates of dose modifications and early treatment discontinuation due to adverse events, which is not uncommon for early-stage ADC trials.
• The TAMARACK study's approach of using lower doses (2.0 mg/kg and 2.7 mg/kg Q4W) is a common strategy to improve tolerability and extend treatment duration, which is a key challenge in ADC development.
• The reported rates of drug interruption (12.6%) and discontinuation (5.3%) in the TAMARACK study for patients on treatment for 12 weeks or who discontinued within 12 weeks compare favorably to the Phase 1 study's rates of 58.5% and 14.6% respectively, suggesting a potential improvement in tolerability.
• Companies like Seagen and ImmunoGen are also developing ADCs for various cancers, and the results of the TAMARACK study will be compared to their ongoing trials and approved products.

Stakeholder Impact

• Shareholders may react positively to the improved safety data and the planned future data releases.
• Patients with mCRPC may benefit from the development of a more tolerable and effective treatment option.
• The medical community will be interested in the updated data and the potential of vobra duo as a treatment for mCRPC.

Next Steps

• MacroGenics plans to release updated interim data, including safety and preliminary efficacy, by the end of May.
• The company also plans to present updated clinical data, including radiographic progression-free survival (rPFS), in the Fall of 2024.

Key Dates

Keywords

vobramitamab duocarmazine, mCRPC, prostate cancer, TAMARACK study, antibody drug conjugate, ADC, B7-H3, clinical trial, safety data, efficacy data