Exelixis prostate plan runs into a double problem

The latest cut of a prostate cancer cohort from Exelixis’s Cosmic-021 trial of Cabometyx plus Tecentriq show a deteriorating dataset, but this is just one of the group’s problems. The second is the upcoming results of Novartis’s Vision study of 177Lu-PSMA-617 in a similar setting; Vision data are under wraps until next month’s Asco meeting, but their selection as a late-breaker hints at a good result. A strong Vision readout would undermine Exelixis’s case for accelerated Cabometyx approval based on Cosmic-021 – even before considering the latter dataset’s deterioration. Exelixis plans a filing in high-risk mCRPC patients progressed on Zytiga or Extandi, but yesterday said an independent review of Cosmic-021 showed overall remission rate of just 18%, which Stifel reckons is not far off what PD-(L)1 blockade alone can do. At Asco-GU in February 2020 Exelixis had boasted a 33% response rate – in a smaller dataset and according to more lenient, investigator review. True, Novartis’s Vision trial gives 177Lu-PSMA-617 on top of Zytiga/Xtandi, but this technical difference will unlikely amount to much if Vision establishes ’617 as a new late-line standard. Evaluate Pharma sellside consensus sees Cabometyx generating $106m of 2026 revenues in prostate cancer, versus $552m for ’617.

High-risk, post-Zytiga/Xtandi patients in Cosmic-021
Data point Median follow-up n ORR CR
Asco-GU, Feb 2020 12.6mth 36 33% 2
May 2021 15.8mth 101 18%* 0*
Source: Exelixis; *by blinded independent review.

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