Update: After patient deaths, FDA puts CTI BioPharma's myelofibrosis on full clinical hold
Update: CTI BioPharma announced on Tuesday that the FDA had placed pacritinib on a full clinical hold, after previously placing the drug on a partial hold. A full clinical hold means all patients must immediately discontinue use of pacritinib and no new patients can be enrolled in trials.
- CTI BioPharma shares plummeted more than 63% in early Monday trading after the FDA issued a partial clinical hold on a phase 3 myelofibrosis medication. CTI's partner on the therapy, Baxalta, dropped more than 3%. The FDA subsequently upgraded the partial hold to full on Tuesday, meaning all patients must discontinue pacritinib immediately.
- Pacritinib is an oral kinase inhibitor that would be the first JAK2 inhibitor approved for treating myelofibrosis, a type of chronic blood cancer.
- Regulators issued the full clinical hold after finding that patients who were in the late-stage study's drug arm were beginning to die at a higher rate and experiencing more adverse events than those in the placebo arm.
Investors reacted swiftly and mercilessly upon learning about the initial partial hold. CTI expounded upon the FDA's decision in a statement.
"The excess mortality was most evident during the non-randomized crossover period following the initial 24 weeks of randomized treatment, during which patients in the control arm could switch to pacritinib treatment," said the company.
"In prior correspondence, the FDA acknowledged the difficulty addressing non-significant results, and that crossover designs can confound the interpretation of safety as well as the evaluation of survival."
There have been a number of cases in which the FDA has issued holds related to medication safety concerns in recent months. Zafgen, which is attempting to create a therapy for the treatment of obesity linked to Prader-Wilii syndrome, was slapped with a complete clinical hold after two patient deaths which may have been associated with the therapy.
The question is: What will a more complete reading of the data demonstrate? As CTI pointed out in its statement, assessing the full significance of the elevated death rate is difficult considering that the most pronounced effect was witnesses during a "crossover" period where patients could switch between the placebo and drug arms of the study.
In January, Shire announced that it would be purchasing Baxalta, which itself is a spinoff of Baxter, for $32 billion.