Takeda Pharmaceutical's (NASDAQOTH: TKPYY) prospective inflammatory bowel agent vedolizumab has hit a hitch in the path to approval.

After filing for approval for the Crohn's disease and ulcerative colitis agent this past summer, Takeda is facing FDA concern over efficaacy as well as the immunosuppressing effects of the drug and the related risk for a lethal brain infection, progressive multifocal leukoencephalopathy, or PML.

The agent was acquired in Takeda's $9 billion buyout of Millennium Pharmaceuticals. In 2012, Takeda issued statements that vedolizumab showed a statistically significant remission in inflammatory bowel disease, but failed to release specific data. The Japanese company filed for U.S. approval in June and finally released the late-stage data in August. The data showed a clinical response to vedolizumab in treatment-resistant patients, as compared to control patients receiving a placebo.

However, the data was more impressive for ulcerative colitis than Crohn's disease. The FDA continues to quibble on if the drug has proven efficacy in the treatment of Crohn's. While both diseases are classified as "inflammatory bowel diseases," they each have distinct pathologies, treatment options, and prognosis (including varied rates of future colon cancer development, the possibility of surgical resection as a curative therapy, and symptomology).

Current therapies for inflammatory bowel disease revolve around steroids and anti-TNF-alpha agents like AbbVie's (ABBV 1.05%) Humira and Johnson and Johnson's (JNJ 0.22%) Remicade -- the latter of which is facing significant competition by biosimilars.These agents work against inflammatory mediators that the body produces in automimmune diseases as well as normal immune system function, making patients subject to opportunistic infections. Around 10% of patients eventually stop responding to therapy as they develop antibodies to the agents.

Vedolizumab aims to avoid these issues. It is a more specific antibody that targets a particular molecule (an integrin) on white blood cells that is relatively unique to the gut. In theory, Takeda's new drug should have specificity that allows it to avoid side effects associated with the immunocompromise of Humira and Remicade.

Nonetheless, the FDA is reviewing the risk of PML in patients taking vedolizumab. While no patients in studies came down with the rare brain infection, vedolizumab works on a similar mechanism to Biogen Idec's (BIIB -1.53%) Tysabri, which carries a black-box warning because of the PML risk. Tysabri is used as a treatment for multiple sclerosis, and Takeda has already drawn distinctions for the FDA on the difference in mechanism between vedolizumab and Tysabri.

An advisory panel this week, however, gave good news for vedolizumab, voting unanimously that the risks of the drug was appropriately represented and that it was safe in regards to PML.

The panel was less agreeable on efficacy of the drug. While they voted 20-0 (one abstained) that it was an appropriate maintenance therapy for Crohn's disease whose benefits outweighed the risks, as an initial "induction" therapy, it was 12-9 that the drug was appropriate. 

A final decision should be announced by the FDA by Feb. 18 on the use of vedolizumab in ulcerative colitis and by June 18 on the use of it in Crohn's.

The bottom line
If approved, vedolizumab could be a potential blockbuster for Takeda. Inflammatory bowel disease is often diagnosed in young adulthood, and treatment becomes lifelong for these patients. The long-term nature of the treatment breeds decades of loyalty and sales. Takeda has tapped six prospects, vedolizumab included, for 2014 approval. Takeda's major diabetes agent Actos has been facing a significant generic challenge since its patent expires and certain needs an approval out of its pipeline to begin mitigating that competition.

Approval is still likely, since it seems that the PML concern is less based on actual data and more based on an association with Biogen Idec's Tysabri. Nonetheless, the FDA has been harsher on safety concerns recently and February could deliver a surprise for Takeda. While the advisory panel is clearly in Takeda's favor when discussing safety, the FDA is not obliged to follow its recommendations, although it usually does.

Approval will be a win for Takeda, but it won't necessarily chip away at AbbVie's sales of Humira. Humira will remain the first-line therapy in IBD and has safety from competition as a major therapy for several other autoimmune diseases such as rheumatoid arthritis as well. Sales of Humira were up 19% in the most recent quarter, and it retains patent protection until 2016. The drug it a critical part of AbbVie's profile, and that is unlikely to change regardless of the development of related agents.