BTK Inhibitors May Be Linked to Pneumocystis jirovecii Pneumonia

Patients with chronic lymphocytic leukemia (CLL) treated with the Bruton’s tyrosine kinase (BTK) inhibitor, ibrutinib, may have a mildly elevated risk of developing Pneumocystis jirovecii pneumonia (PCP), according to an article published in Blood.¹

Among 96 patients treated only with ibrutinib, researchers observed 5 cases of PCP; after initiating ibrutinib treatment, median time to PCP occurrence was 6 months. PCP diagnosis, however, was often delayed.

CD4 T-cell counts and immunoglobulin G levels were within normal ranges for patients with PCP, suggesting that ibrutinib was not interfering with normal immune functions.

The authors conclude, though inconclusively, that PCP incidence may be related to BTK inhibition, suggesting a need for caution about or prophylaxis for PCP for patients receiving BTK inhibitors.

All cases of PCP, which were grade 2 or lower, were resolved with oral therapies; there were no recorded cases of recurrence.

Reference

1. Ahn IE, Jerussi T, Farooqui M, Tian X, Wiestner A, Gea-Banacloche J. Atypical Pneumocystis jirovecii pneumonia in previously untreated patients with CLL on single-agent ibrutinib. Blood. 2016 Aug 8. doi: 10.1182/blood-2016-06-722991 [Epub ahead of print]