On 28 March 2019, Gilead and Galapagos announced that their selective JAK1 inhibitor, rheumatoid arthritis (RA) drug filgotinib , had met all primary endpoints in its two remaining Phase III trials, Finch 1 and FINCH 3.

The FINCH 1 and 3 studies build on data from FINCH 2 and strongly demonstrate that filgotinib is safe and effective in a wide range of patients with rheumatoid arthritis (RA)—from new patients initiating their first therapy to patients with recalcitrant disease who have cycled through one or more biologics.

GlobalData believes that one of the most important aspects of the new FINCH 1 and FINCH 3 data was that they replicated the exceptional safety profile demonstrated by the drug in FINCH 2 while still retaining good efficacy. Not only did filgotinib treatment avoid imparting increased risk of cardiovascular issues such as venous thrombosis or pulmonary embolism, an ongoing worry for agents in the JAK inhibitor drug class, it also appeared to minimise the risk of immune system compromise.

In a pooled safety analysis of all three Phase III trials, there was only a small increase in the rate of serious infections (1.0% vs. 1.4%) and herpes zoster infection (0.4% vs. 0.6%) between placebo and filgotinib-treated groups.

When compared to adalimumab (a comparator drug assessed in FINCH 1), filgotinib-treated groups demonstrated a lower rate of serious infections (2.5% vs. 1.4%) and an equivalent rate of herpes zoster infection.

Finally, compared to both placebo- and adalimumab-treated groups, the rate of malignancy in filgotinib-treated groups was negligible (0.4% for placebo vs. 0.3% for adalimumab and <0.1% for filgotinib).

In the future, these safety findings may set filgotinib apart from competitors as a safer option for patients who are immunocompromised. However, it is important to note that there are several crucial pieces of safety data that Gilead and Galapagos have not yet shared for the FINCH 1 and 3 trials, including the overall rate of adverse events, rate of adverse events leading to study discontinuation, the overall rate of infection, the rate of opportunistic infections, as well as changes in key hematological parameters including platelets and hemoglobin. All of these parameters were promising in FINCH 2, and if replicated in FINCH 1 and 3, would further bolster filgotinib’s case as a safer therapeutic option.

Despite these excellent Phase III data, GlobalData believes that filgotinib still has a challenging road ahead. Particularly, it needs to contend with competition from AbbVie ’s selective JAK1 inhibitor candidate, upadacitinib, which has a substantial head start on filgotinib. Not only has AbbVie already submitted marketing applications for upadacitinib in both the US and EU (in December 2018), but based on these recent topline data for filgotinib, upadacitinib may still hold the upper hand when it comes to efficacy. In particular, upadacitinib demonstrated statistically significant superiority over adalimumab across nearly all efficacy endpoints in the SELECT-COMPARE trial, while in FINCH 1, filgotinib was superior to adalimumab in only one endpoint at the highest dose of the drug.

Additionally, it is still unclear when Gilead and Galapagos will be able to file for marketing authorisation.

While there are no apparent barriers to filing in the EU, US filing still hinges on the completion of the FINCH testicular safety study. This study was begun in 2016 but, according to an investor presentation last year, has been facing difficulties with recruitment.

According to GlobalData’s recent report “Rheumatoid Arthritis: Market Analysis and Forecasts to 2027,” upadacitinib and filgotinib are expected to achieve sales of $880M and $396M, respectively, by 2027. As nearly 80% of these sales are projected to come from the US, if the final FINCH trial continues to bottle-neck FDA approval, it could severely limit filgotinib’s future.

Based on data released from FINCH 1, 2, and 3, on top of being very effective, filgotinib demonstrates a strong safety profile.

However, GlobalData notes that despite this success, competition from upadacitinib remains a very real threat. With upadacitinib’s head start on filing in the US and EU and potential edge on efficacy, Gilead and Galapagos are going to have to hustle to secure filgotinib a strong position in the immunology marketplace.