Protein kinase C beta (PKCβ), a pivotal enzyme in B-cell signaling and survival, is overexpressed in most cases of mantle cell lymphoma (MCL). Activation of PI3K/AKT pathway is involved in pathogenesis of MCL. Enzastaurin, an oral serine/threonine kinase inhibitor, suppresses signaling through PKCβ/PI3K/AKT pathways, induces apoptosis, reduces proliferation, and suppresses tumor-induced angiogenesis.
Patients and methods
Patients with relapsed/refractory MCL, and no more than four regimens of prior therapy, received 500 mg enzastaurin, orally, once daily.
Results
Sixty patients, median age 66 years (range 45–85), Eastern Cooperative Oncology Group performance status of zero to two (48% had baseline International Prognostic Index of 3–5), were enrolled. Most patients had prior CHOP-like chemotherapy and/or rituximab (median = 2 regimens). No drug-related deaths occurred. There was one case each of grade 3 anemia, diarrhea, dyspnea, vomiting, hypotension, and syncope. Fatigue was the most common toxicity. Although no objective tumor responses occurred, 22 patients (37%, 95% CI 25% to 49%) were free from progression (FFP) for ≥3 cycles (one cycle = 28 days); 6 of 22 were FFP for >6 months. Two patients remain on treatment and FFP at >23 months.
Conclusion
Freedom from progression for >6 months in six patients and a favorable toxicity profile with minimal hematological toxicity indicate that enzastaurin warrants evaluation as maintenance therapy and combination chemotherapy in MCL.