Mirati and the elephant in the room

The sellside’s support for Mirati in the wake of the group’s latest delay for adagrasib is admirable, but it ignores one very large problem. To wit: after a standard 10-month review, Mirati will be seeking accelerated approval for adagrasib – on the surrogate endpoint of remission rates – at a time when Amgen’s rival Lumakras will have yielded confirmatory survival data. At worst Lumakras might already have secured full approval by this point, destroying the basis for an accelerated adagrasib approval. After already losing 12 months to Amgen Mirati had been hoping for a priority six-month review, and investors can ignore the new risk at their peril. Yesterday Stifel said drugs could still be greenlit before their Pdufa dates; Leerink called the FDA’s decision to hold Mirati to standard review “perplexing”, and even suggested the agency’s Covid-related backlog as a reason. This overlooks the fact that in the middle of the pandemic Lumakras’s filing had been turned around in just three months, and that last year Agenus had to pull an accelerated filing once Merck & Co secured full approval for a similar drug in a similar indication. With Lumakras already available the FDA might simply not consider adagrasib a priority.

Timeline of the duelling Kras G12C inhibitors in lung cancer
  Lumakras (Amgen) Adagrasib (Mirati)
Accelerated filing for 2L Kras G12C+ve NSCLC accepted 16 Feb 2021 15 Feb 2022
Goal action date 16 Aug 2021 (priority review) 14 Dec 2022 (standard review)
Accelerated US approval 28 May 2021 Late 2022*
Confirmatory study readout H2 2022 (Codebreak-200) H2 2023 (Krystal-12)
Full US approval Possible in H2 2022 2023/24
Note: *assumes that this option remains open; if not the FDA will likely wait until confirmatory survival data from Krystal-12. Source: company statements.

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