Wall Street is buzzing about Gilead's rheumatoid arthritis drug. Here's why

Stocks of Belgian biotechnology Galapagos NV increased 24% Friday after the company, along with pharmaceutical giant Gilead Sciences Inc., announced that two phase 3 studies of their study rheumatoid arthritis drug had achieved their primary endpoints.

But what really had Wall Street excited was the fabric's safety profile. Filgotinib is an oral, selective JAK inhibitor, a class of drug that has been anchored for safety reasons. JAK inhibitors, including Eli Lilly & Co

LLY, + 0.61%

Olumiant and Pfizer Inc. s

PFE, + 0.43%

Xeljanz, may have serious side effects, including increased risk of serious infections, malignancies and in Olumiant's case for cardiovascular events such as deep vein thrombosis and pulmonary embolism.

But filgotinib, like Galapagos

GLPG, + 22.50%

evolves with Gilead

GILD, + 2.07%

showed promising safety data, while showing similar efficiencies for the competitors.

Gilead shares accounted for 2.8% in afternoon trading. Galapagos US listed shares were on their way to closing at the highest level since September 2018.

Read : Prescription drug prices don't rise – they fall for the first time in 47 years

Also ]: Shoppers will have prescription drugs from Amazon, medical marijuana and cryptocurrency

"FINCH 1 & 3 confirms filgotinib's best security profile," JP Morgan analysts wrote in a note Friday, referring to the two trials by name.

In a test, the researchers on filgotinib alone and in combination with methotrexate saw a major pill treatment in patients who had never previously been treated with methotrexate. After 24 weeks, a greater proportion of patients on combination therapy showed an improvement in the number of sore and swollen joints (greater than 20%), a target that called ACR20, which was the primary endpoint of the experiment, than in methotrexate alone.

In another experiment, the researchers looked at how two different doses of filgotinib held up against AbbVie Inc.

ABBV, + 0.80% best-selling Humira or methotrexate. This time, patients were enrolled in the trial already treated with methotrexate, but had not responded adequately to the drug.

After 12 weeks, the proportion of patients receiving ACR20 was higher in the filgotinib group than in the methotrexate group. However, in most cases, filgotinib patients did not show statistically significant improvement over those in Humira. Exception: A larger proportion of patients on filgotinib achieved clinical remission than in Humira.

What really got Wall Street's eye was filgotinib's security data. Data from three phase 3 studies showed that among patients already receiving methotrexate, 1.5% of those receiving higher doses of filgotinib had severe infections as an adverse event compared to 2.5% of those receiving Humira. And none of the patients on the higher dose of filgotinib had malignancies, compared to 0.3% of Humira.

Filgotinib's security profile is important for investors. There are other JAK inhibitors on the market, and the food and drug administration is undergoing a new drug application which AbbVie submitted in December for its own JAK inhibitor, called upadacitinib. Filgotinib's safety data is what can differentiate it from the others.

"Since filgotinib is likely to be the fourth JAKi to the market, a clean security profile can help drive usage," Jefferies analysts said in a Friday match.

Don't miss : Increasing cost of new special drugs next cutting edge in war against high prescription rates

Some analysts were excited about how filgotinib's safety data compared to AbbVies oppadacitinib. The Gilead and Galapagos trials did not compare filgotinib directly with upadacitinib, but analysts at J.P. Morgan said they believed filgotinib's safety data looked stronger, especially when it comes to deep vein thrombosis and pulmonary embolism.

However, unlike filgotinib, upadacitinib showed a better effect than Humira on several measures, "which may be a small market dependency for filgotinib," wrote J.P. Morgan analysts.

Filgotinib's trial results come at a time when Gilead, including sliding hepatitis C drugs, is looking for new ways to expand their business. Shares in the pharmaceutical giant have fallen 13% over the last 12 months, while S & P 500

SPX, + 0.67%

has increased 7%. Shares in Galapagos have increased 19%.