Pirtobrutinib: A New and Distinctive Treatment Option for B-Cell Malignancies

Objective: The objective was to evaluate the efficacy/safety of pirtobrutinib in the treatment of B-cell malignancies and distinguish it from other available Bruton’s tyrosine kinase (BTK) inhibitors. Data sources: A literature search of PubMed (January 2021 through November 2023) and Clinicaltrials.gov was conducted using terms pirtobrutinib, Jaypirca, and LOXO 305. Licensing trials of available BTK inhibitors were also reviewed. Study selection and data extraction: Relevant English-language clinical trials were evaluated. Data synthesis: Pirtobrutinib was approved by the US Food and Drug Administration for the treatment of relapsed/refractory mantle cell lymphoma (MCL) and chronic lymphocytic leukemia (CLL) based largely on a phase 1/2 study in B-cell malignancies. Pirtobrutinib demonstrated a 73% overall response rate (ORR) in the CLL population and 58% in MCL. Pirtobrutinib has activity in patients resistant to earlier-generation, covalent BTK inhibitors. In fact, the ORRs were similar in BTK-pretreated and naïve patients. Adverse effects include fatigue, diarrhea, bleeding, and infection. Atrial fibrillation, a class effect of BTK inhibitors, may be less common with pirtobrutinib. Relevance to patient care and clinical practice in comparison with existing drugs: Compared with earlier-generation BTK inhibitors, pirtobrutinib is more selective for BTK and binds noncovalently to the receptor. Ongoing studies are evaluating pirtobrutinib’s use in multiple B-cell malignancies and comparing it with other BTK inhibitors. Conclusion: The characteristics of pirtobrutinib render it useful in the treatment of B-cell malignancies no longer responding to a previous BTK inhibitor, and results from ongoing clinical trials may support future expanded use.