MacroGenics (NASDAQ: MGNX) stock plummeted about 80% in intraday trading Friday following reports of multiple fatalities and over 50% of grade 3 or higher adverse events in its cancer drug trial.
MacroGenics (MGNX), a leading biopharmaceutical company, recently shared interim findings from the TAMARACK Phase 2 study of vobramitamab duocarmazine (vobra duo), a novel therapeutic agent targeting B7-H3, an antigen with broad expression across multiple solid tumors. The study primarily focuses on previously treated patients with metastatic castration-resistant prostate cancer (mCRPC).
Trial Results and Adverse Events Analysis
The latest data (as of the data cut-off date of April 12, 2024), reveals a noteworthy occurrence of adverse events during the trial, with five reported deaths and over a 50% rate of grade 3 or worse adverse events observed in both dose cohorts (2 mg/kg and 2.7 mg/kg administered every four weeks).
Comparing the recent data with earlier findings from January 4, 2024, significant fluctuations in treatment-emergent adverse events (TEAEs) rates have been noted. Specifically, the rates of TEAEs were 54.4% and 51.2% for the low (2.0 mg/kg) and high (2.7 mg/kg q4W) dose arms, respectively, during the recent data cut-off. In contrast, the earlier data reported rates of 25.3% and 31.4%, respectively.
Moreover, the latest readout highlights a substantial increase in TEAE-related interruptions, reaching 42.2% and 55.8% in the low and high-dose cohorts, respectively, compared to 11% and 18.6% reported in earlier data.
Notably, investigators have identified two cardiovascular deaths, one in each study group, as unrelated to the investigational drug. However, three deaths at the higher dose are currently under investigation, with two of these patients succumbing to pneumonitis.
Despite these setbacks, the interim analysis unveiled promising indicators of therapeutic efficacy. The overall response rates stood at 17.8% and 25.0% in the low and high-dose arms, respectively, with the inclusion of patients exhibiting unconfirmed responses elevating these figures to 24.4% and 43.8%.
Furthermore, the vobra duo showcased notable efficacy in prostate-specific antigen (PSA) reduction, with over 50% reductions observed in 50% and 50.7% of patients in the 2.0 mg/kg and 2.7 mg/kg arms, respectively. Confirmed PSA reduction rates stood at 43.9% and 36.6%, demonstrating a favorable impact on disease biomarkers.
MacroGenics (NASDAQ: MGNX) Stock Reaction
MGNX stock plunged 77.44% to close at $3.31 on Friday. Its value decreased by 78.88% this week. Trading activity has witnessed 35,148,360 (35.14 million) shares changing hands, well above the average daily volume of 2.02 million.
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