MacroGenics Shares Fall After MGC018 Data Fails To Impress At ESMO Presentation

MacroGenics Inc MGNX announced preliminary safety and anti-tumor activity data from dose-expansion cohorts of the Phase 1 trial of MGC018. The data was presented at the 2021 European Society for Medical Oncology (ESMO21) Virtual Conference.

Data: 39 metastatic castration-resistant prostate cancer (mCRPC) patients were evaluable for prostate-specific antigen (PSA) response. Reductions in PSA levels of over 50% were observed in 21 of 39 patients. 24 of the 39 patients (62%) remained on treatment.

Of the 40 patients in the metastatic castration-resistant prostate cancer (mCRPC) cohort, 16 of the 23 patients with measurable disease were evaluable for tumor response. 10 of 16 patients (63%) had reductions in their target lesion sums from baseline. 

Four patients (25%) demonstrated a partial response (PR), including two confirmed and two unconfirmed PRs.

The non-small cell lung cancer (NSCLC) cohort expansion had been fully enrolled with 21 patients. A total of 16 NSCLC patients were evaluable for tumor response by RECIST. 13 of 16 (81%) patients had reductions in their target lesion sums from baseline. 

Four of these 16 patients (25%) experienced unconfirmed partial responses. Another one of these 16 patients experienced a 30% reduction in target lesions.

MacroGenics also announced results from Cohort A Part 1 of the Phase 2/3 MAHOGANY trial of Margenza (margetuximab-cmkb).

Related: MacroGenics' Cancer Drug Margenza Flops On Overall Survival Analysis

Impact: Tumor shrinkage was observed in 32 of 41 patients (78%) with at least one post-baseline target lesion measurement. 21 of 40 response-evaluable patients achieved an objective response, including four confirmed complete responses and 17 confirmed partial responses. 

29 of 40 patients achieved disease control, and the median duration of response was 10.3 months. 

Median progression-free survival (PFS) was 6.4 months by independent assessment; median overall survival (OS) was not reached. At both 12 and 18 months, OS was 85%.

Price Action: MGNX stock is down 25.90% at $20.40 during the market session on the last check Thursday.

Check out our coverage of the European Society for Medical Oncology Congress (ESMO21).