More Sophia data deal Macrogenics’ partnering hopes another blow

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Things have gone from bad to worse for Macrogenics. Not only did a second interim analysis of the Sophia Her2-positive breast cancer trial fail to show an improvement in median overall survival with the group’s lead asset, margetuximab, a previously seen benefit in a genetic subgroup also shrank. Macrogenics’ hopes of finding a partner, already slim after initial Sophia data at this year’s Asco, now look even slimmer. Investors sent the company’s stock down as much as 15% in premarket trading today despite the sellside noting an improvement in the hazard ratios in both the intent-to-treat population and subjects with the CD16A/158F allele, a genetic variant found in around 85% of patients that is associated with poor response to Herceptin. Macrogenics will report more data at the San Antonio Breast Cancer Symposium in December, and a final overall survival analysis is due once 385 deaths have occurred, expected by mid-2020. The company plans a filing with the US FDA by the end of the year, which will include the latest OS data but, even if approved, margetuximab could have a hard time commercially, with the race to design a “better Herceptin” looking increasingly competitive.

Median overall survival data from Sophia interim analyses
Oct 2019 (270 events) Margetuximab Herceptin  Difference Hazard ratio
mOS – ITT population 21.6 months 19.8 months 1.8 months 0.89 (p=0.326)
mOS – CD16A 158F allele* 23.7 months 19.4 months 4.3 months 0.79 (p=0.087)
         
Asco 2019 (158 events) Margetuximab Herceptin  Difference Hazard ratio
mOS – ITT population 18.9 months 17.2 months 1.7 months 0.95
mOS – CD16A 158F allele 23.6 months 16.9 months 6.7 months 0.82
*Pre-specified, exploratory analysis. Source: company releases.

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