Anthos goes pivotal as Novartis and Pfizer look on

In about 18 months' time Novartis will find out whether it made a mistake to give up on the blood-thinning project abelacimab. The MAb, spun out into the Blackstone-backed Anthos Therapeutics in 2019, yesterday became the first factor XI inhibitor to begin phase 3 patient enrolment. Two pivotal studies, Aster and Magnolia, are now under way, both with primary completion dates of September 2023. The mechanism (abelacimab also hits factor XIa) is an unusual area of research, featuring a small handful of big players, with Bayer and Bristol Myers Squibb working on several distinct assets. Both have franchises to defend: the former’s Xarelto loses US patent protection in 2024, while the latter’s Eliquis will likely go two years later. Unusually, Bristol’s Eliquis partner Pfizer is not active in factor XI, and was asked about this on its first-quarter call. It said: "We really want to see a similar step-up in breakthrough potential as we saw with Eliquis. And we haven't yet been convinced about that step-up, but we are carefully monitoring." The Aster study compares abelacimab head to head against Eliquis, so the answer – for Novartis and Pfizer alike – will come soon enough.