Merck announced data for their Phase 3 cough program this morning and it was rather disappointing. Cough effect in Phase 3 saw a large decrease from Phase 2 and taste disturbance was the same. Remember, we used Merck 's cough data as a comparable for Bellus (BLU). Merck acquired the gefapixant candidate for $500M upfront + $750M in milestones.
A total of 2,044 participants were treated in two separate studies: COUGH-1 (n=730) and COUGH-2 (n=1,314). In both studies, patients were in one of three groups: gefapixant 45 mg twice daily, gefapixant 15 mg twice daily, or placebo. The 15mg dose was not statistically significant vs placebo, so we will focus on 45mg dose.
In the 2 Phase 3 studies, 45mg of gefapixant demonstrated a ~15%-18% cough reduction vs placebo. In Phase 2, this same placebo reduction figure was 37%. So, the cough effect was nearly cut in half from Phase 2 to Phase 3. Additionally, 58-69% of patients reported a taste disturbance in the two Phase 3 studies, which were in line with Phase 2 data.
Merck’s gefapixant is the furthest along P2X3 candidate in chronic cough. Other P2X3 candidates from Bayer, Shionogi and Bellus have reported Phase 2 data, but none have really stood out (see Phase 2 data points below).
Most likely, Merck will get FDA approval for gefapixant, which will set the new benchmark for Phase 3 data: at least 15% placebo adjusted cough reduction and taste disturbances less than 60%.
This brings up the concerns that maybe P2X3 is not the promising treatment in chronic cough that it was once touted as. Actual data has come below expectations in several studies now.
PropThink contributors have NO POSITION in any of the companies mentioned above.
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