US FDA will continue to tie orphan exclusivity to uses or indications for which the drug was approved. Attorneys say this buys agency time to sort out complex policy and legal questions and continue to seek legislative fix. Additional litigation is also possible, as happened in Depomed case.

DC Circuit Court upholds FDA’s grant of new chemical entity exclusivity to Sanofi’s multiple sclerosis drug Aubagio (teriflunomide) even though the agency had previously approved teriflunomide as an impurity in Sanofi’s Arava (leflunomide). FDA reviews known impurities in drugs only to assess their impact on safety and efficacy, not to approve them, court says.

FDA didn’t get policy rider it wanted which would have reversed the Catalyst court ruling that the agency cannot limit a drug’s orphan exclusivity to its approved indication. One attorney says the clearest path forward is for FDA to issue new rulemaking and face additional litigation.

Already partnered on antibody-drug conjugates and a Phase III breast cancer candidate, Merck could pay up to $9.3bn under its third pact in 2022 with Kelun. Eisai divests Fycompa to Catalyst.