After Reporting Five Patient Deaths, Data Committee Recommends MacroGenics Halt Prostate Cancer Trial

MacroGenics Inc. MGNX announced on Tuesday that it reviewed data accumulated from the TAMARACK Phase 2 study of vobramitamab duocarmazine (vobra duo).

In May, when the company released interim data from the trial, MacroGenics reported five deaths (fatal outcome) during the trial.

After reviewing, MacroGenics agreed with the study’s Independent Data Monitoring Committee’s recommendation to discontinue the treatment for the remaining metastatic castration-resistant prostate cancer (mCRPC) study participants who could have received additional doses.

Most of these remaining study participants had already received 8-12 cycles of vobra duo. Participants continue to be monitored for adverse events, disease progression and survival.

“We decided to discontinue additional dosing for the remaining TAMARACK participants who had not yet completed treatment. We expect to have the data necessary to determine next steps for the vobra duo program later this year and will provide further updates on an investor call following our ESMO presentation,” said Dr. Scott Koenig, president and CEO of MacroGenics.

The company expects to have the mature efficacy findings, including median rPFS, later in the second half of 2024 and plans to present the data at a subsequent medical conference.

The company also announced a poster (display) presentation of clinical data from the TAMARACK Phase 2 study of vobra duo at the upcoming European Society for Medical Oncology (ESMO) Congress 2024.

The abstract was based on an April 12 data cutoff, and the poster will report additional data from a July 9 data cutoff, including safety, efficacy, and landmark 6-month radiographic progression-free survival (rPFS) data.

MacroGenics completed enrollment in the TAMARACK study in the fourth quarter of 2023 and plans to present the study’s landmark primary endpoint, the 6-month rPFS rate, which represents the proportion of study participants who remain alive and progression-free at six months.

Concurrently, MacroGenics achieved $100 million in milestones from Incyte Corporation INCY related to the development progress of Zynyz (retifanlimabz), following an agreement on July 24. Zynyz is indicated in the U.S. for metastatic or recurrent locally advanced Merkel cell carcinoma.

Analyst Reactions:

• B. Riley Securities downgraded Macrogenics from Buy to Neutral and lowered the price target from $18 to $5.
• Guggenheim downgraded Macrogenics from Buy to Neutral.
• Barclays maintained Macrogenics with an Overweight and lowered the price target from $9 to $8.

MGNX Price Action: MacroGenics stock is down 28.59% at $3.75 at last check Wednesday.

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