Gilead Sciences Inc. shares dropped 2.1% in moderate Thursday trade after a Food and Drug Administration briefing document raised safety questions about a similar Eli Lilly & Co. and Incyte Corp. drug. Like Eli Lilly and Incyte, Gilead is also developing a drug, filgotinib, for rheumatoid arthritis in the same class of drugs, called JAK inhibitors, which refers to proteins called Janus-associated kinases that the drugs block. Galapagos NV , from which Gilead licensed the drug and which has co-promotion rights for it in Europe, had shares rise 0.7% in heavy trade. The Eli Lilly and Incyte drug, baricitinib, will go up before a Food and Drug Administration advisory committee meeting on Monday. “Despite this scrutiny, we do not see major read-throughs either way for filgotinib — on one hand, reviewers made a point that thrombosis is likely not a class effect, suggesting they will consider each drug’s profile individually, though on the other hand, the documents do highlight the high safety bar in [rheumatoid arthritis],” said RBC Capital Markets analyst Brian Abrahams. Gilead shares have dropped 1.6% month-to-date and Galapagos shares have dropped 1.9%, compared with a 1.8% rise in the S&P 500 .