The FDA extended the review for AbbVie's (ABBV 1.11%) Rinvoq as a treatment for psoriatic arthritis. On the surface, a three-month delay isn't a huge deal for the large drugmaker. But as Fool.com Contributors Brian Orelli and Keith Speights discuss in this video from Motley Fool Live, recorded on March 22, the extension could be a sign the agency is worried about the side effects of Rinvoq and other JAK inhibitors.

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Brian Orelli: So, last week, AbbVie said that the FDA is extending its review of Rinvoq as a treatment for psoriatic arthritis. On the surface, this isn't really that big of a deal, the FDA often requests data during its review and if it's too much data, the FDA has the right to extend the review period by three months.

But AbbVie said it was due to the FDA requesting "updated assessment of the risk-benefit profile," which doesn't sound too promising. They've received a similar request from the FDA related to the application for atopic dermatitis. Rinvoq is a JAK inhibitor, which is a class of drugs, that's had some issues with side effects. Can you talk about the history of JAK inhibitors and why there may be more than meets the eye to this FDA request?

Keith Speights: Yeah. I think it is that history of JAK inhibitors that makes this more concerning that it might otherwise be. If you go way back, there are several JAK inhibitors that have already been approved. Pfizer's (PFE 0.32%) Xeljanz, for example, was approved back in 2012, I think, for treating rheumatoid arthritis. Incyte (INCY -1.00%) developed a drug that Lilly (LLY 1.15%) licensed and they ultimately won approval for it in rheumatoid arthritis in 2018, that drug is called Olumiant. Both of those are JAK inhibitors and both received black box warnings on their labels related to blood-clotting or thrombosis. For viewers who are not familiar with what those black box labels are, they're the most serious FDA warnings about safety. They don't prevent the drug from being approved, but if you read that label, let's say the reason why it's called black box is it is I think black box around this serious safety warning. Both of these drugs received those black box warnings.

But that's not the only problem. Pfizer received approval for Xeljanz, of course. Earlier this year, Pfizer reported results from a post-marketing safety study that they were required to conduct and Xeljanz flopped. More patients taking Xeljanz had cardiovascular events, more developed cancer than did patients in the real-world who took TNF inhibitors, such as Humira and Enbrel. That was really concerning and that raise more questions about JAK inhibitors as a class.

Last year, Gilead Sciences (GILD 0.54%) tried to get FDA approval of a drug that it had licensed from Galapagos (NASDAQ:GLPG) that's called filgotinib. They were looking for rheumatoid arthritis approval there. It also was a JAK inhibitor and the FDA rejected the drug because of safety concerns. There's definitely a murky history of JAK inhibitors.

Now, Rinvoq has already been approved for one indication. It's already been approved actually in 2019 for treating rheumatoid arthritis. I think the real thing here, Brian, is the AbbVie has a lot riding on these additional approvals for Rinvoq. The company is counting on combined peak sales in the ballpark of $15 billion for Rinvoq and another relatively new autoimmune disease drug that it has on the market called Skyrizi.

Those psoriatic arthritis and atopic dermatitis indications are pretty lucrative. I've seen analysts estimate that those two indications could be worth around $4 billion annually in sales. That's a pretty big chunk of change that AbbVie is hoping to count on. This raises the question as to whether or not they'll get approval for these indications. Now, AbbVie says, publicly, that it's confident in the filings for Rinvoq. Of course, that's exactly what you'd expect the company to say. I would guess they'll probably still want approval, but I wouldn't say it's 100 percent the probability of it because this does raise some serious questions.

Orelli: Yeah. I think the FDA is really looking into this JAK inhibitors and wants to make sure that they're approving them only for the most serious conditions. Something like atopic dermatitis, there's a lot of other options and then also, it's a skin problem. Certainly, my wife has it and it's not fun, but it's also not life-threatening and so you don't want to give them something that has a chance of killing them to treat something that isn't nearly as bad.

Speights: I would say though, AbbVie, they know their game here. They've been in this autoimmune disease market for a long time. Humira has been the best selling drugs in the world for several years. So if any company can get an approval for a JAK inhibitor for these indications, I think it would be AbbVie. By the way, I also want shares of AbbVie, so I'm probably biased to some degree there, but I do think AbbVie has a great track record on this front. So if any company is going to win approvals, I think it will be AbbVie, but I don't think it's a slam dunk.