This from Bank of America Merrill Lynch:
PML association seems very unlikely
INCY disclosed in an 8K today that one patient treated with Jakafi was diagnosed
with PML, a rare debilitating and often fatal brain disease. While there is
significant investor sensitivity to PML specifically and to safety concerns with
drugs, this particular case is not concerning to us, and we feel the stock reaction
to this news is unwarranted. Importantly, neither the duration on drug or
mechanism of action suggest a reasonable disease link to Jakafi. Furthermore,
the incidence rate (1:10,000) also supports the conclusion this PML case was a
random event. Specific details:
- The patient received Jakafi on July 10, 2012, and first presented clinical
symptoms associated with PML in Aug 2012. A definitive diagnosis using brain
biopsy was made in December.
- Typical time to PML with drugs showing a clear link to PML induction (Tysabri
and Raptiva) occur 12-36 months on drug.
- Baseline blood counts are not currently available for the patient, but he had low
T cell counts (300-350), and was leukopenic during follow up.
- Jakafi is myelosuppressive, but does not modulate t cell trafficking, which is
thought to be an important PML driver.
You're better informed than I am. Agreed that the timing makes causation by Jakafi ALMOST impossible. Not so sure of the mechanistic argument because JAK signaling is functionally disconnected from the pathways it is part of. It COULD turn up in single unrelated functions, especially in brain where so many other signal pathways are reused in unique ways.
Do we know what happened procedurally between definitive diagnosis and now? That could be important too.