Celgene's myelofibrosis win represents an expensive green light

Last week’s US approval of fedratinib for myelofibrosis, a project that Celgene bought for an initial $1.1bn in early 2018, provides validation of sorts for the big biotech’s much-maligned business development track record. However, a closer look at the Jak 2 inhibitor, now branded Inrebic, shows why the company deserves some of the criticism. Inrebic has a black box warning for encephalopathy, including Wernicke’s, a signal that was well appreciated at the time of the Celgene buyout; hepatic and gastrointestinal toxicities also differentiate Inrebic from Jakafi, the blockbuster Jak 1/2 inhibitor from Incyte and Novartis that dominates the myelofibrosis space. Jakafi carries its own concerns but Inrebic’s toxicity profile will surely restrict its use; comparing the two agents’ efficacy data, with all the usual caveats, only reinforces this image. Myelofibrosis might be underserved – and not all patients respond to Jakafi – but ending up with a second-line agent was presumably not Celgene’s intention. It is therefore hard to see how the top-dollar up-front fee, and $1.4bn due in regulatory milestones, will be recouped. Consensus from EvaluatePharma has sales of $378m by 2024, a figure that could well be trimmed once analysts take a fresh look at Inrebic’s prospects.

Cross trial comparison of Jakafi and Inrebic 
  Inrebic – Jakarta study Jakafi – Study 1 and Study 2
  Inrebic (n=96) Placebo (n=96) Jakafi (n=155) Placebo (n=154) Jakafi (n=146) Best available therapy (n=73)
Number (%) of patients with spleen volume reduction by 35% or more 35 (37) 1 (1) 65 (42) 1 (<1) 41 (29) 0
Source: US drug labels.

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