A phase 2 trial of Gilead and Galapagos’ JAK1 inhibitor filgotinib has met its primary endpoint. The results position the potential blockbuster to advance into phase 3 in ankylosing spondylitis, although a safety signal gave investors a scare.
Filgotinib is racing AbbVie’s rival JAK1 inhibitor upadacitinib to market in a range of indications, most notably rheumatoid arthritis. Both drugs ceded a sizable head start to Eli Lilly and Incyte’s JAK drug Olumiant, but early clinical data suggested they may have a better safety profile. Olumiant is linked to safety issues including an increased risk of deep venous thrombosis (DVT).
Gilead and Galapagos’ filgotinib looked to be free from these issues, but one patient in the phase 2 ankylosing spondylitis trial suffered a non-serious DVT. Galapagos’ share price dipped following news of the DVT case, despite otherwise positive data from the phase 2. However, the stock regained some of the lost ground as a clearer picture of the DVT case emerged.
“Importantly, we understand this patient had an inherited risk of thrombosis (Factor V Leiden gene mutation) and the DVT occurred in the follow-up period post-treatment, hence was later assessed to not be treatment-related,” Jefferies analyst Peter Welford wrote in a note to investors.
The reaction of the stock to the DVT case reflects the importance of safety to filgotinib. By the time filgotinib gets to market, doctors will already be able to choose between several other JAK inhibitors. If these drugs have comparable efficacy, safety will emerge as a key battleground. Aside from worries about testicular toxicity, filgotinib has looked well set to compete on the safety front. A case of DVT linked to the drug would have diminished the strength of Gilead and Galapagos’ hand.
Other aspects of the phase 2 ankylosing spondylitis data were positive. The trial linked filgotinib to statistically significant improvements on a disease activity score and response rate, encouraging Gilead and Galapagos to commit to running a phase 3 in the indication.
Ankylosing spondylitis is one of a clutch of relatively minor opportunities Gilead and Galapagos are pursuing as they explore the full potential of filgotinib. The bigger prize is rheumatoid arthritis. Data from a trial of filgotinib in the indication are due imminently.