CHICAGO–Polatuzumab plus rituximab in relapsed/refractory follicular lymphoma showed high overall response rates at two doses of polatuzumab, with a higher complete response rate at 2.4 mg/kg, data presented at the 2015 American Society of Clinical Oncology (ASCO) annual meeting have shown.
Polatuzumab vedotin is a potent microtubule inhibitor CD79b monoclonal antibody. “Clinical activity has been observed in relapsed/refractory NHL at 8 mg/kg every 3 weeks in phase I trials…but the optimal duration of therapy is unknown,” said Ranjana Advani, MD, of the Division of Oncology at Stanford University School of Medicine in Stanford, CA.
Researchers enrolled 45 patients with relapsed/refractory follicular lymphoma and assigned them to receive polatuzumab at 2.4 mg/kg or 1.8 mg/kg with rituximab 375 mg/m2 every 21 days until disease progression or unacceptable toxicity.
Results showed that overall response rates were 76% (19/25) and 75% (15/20) in the 2.4 mg/kg and 1.8 mg/kg groups, respectively. Researchers found that after eight cycles of immunotherapy, complete response rates were 28% at 2.4 mg/kg and 10% at 1.8 mg/kg.
Median progression-free survival was 15 months (95% CI: 11, NE) in the 2.4 mg/kg groups and not reached (95% CI: 9.9, NE) in the 1.8 mg/kg group.
“A higher response rate was observed with higher polatuzumab dose level and longer treatment duration,” Dr. Advani added.
In regard to safety, serious adverse events and discontinuation rates were less frequent in patients who received eight cycles compared with all patients and were less frequent in the 1.8 mg/kg group than the 2.4 mg/kg group.
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Of note, a higher proportion of patients in the 1.8 mg/kg group experienced grade 1 peripheral neuropathy, while a higher proportion of patients in the 2.4 mg/kg group experienced grade 2 peripheral neuropathy.
The findings suggest that the safety of polatuzumab can be improved by reducing the treatment duration and/or lowering the dose of polatuzumab.
“Polatuzumab vedotin may represent a clinically meaningful treatment option for patients with NHL at 1.8 mg/kg with a fixed duration of 8 cycles or less. Studies of polatuzumab vedotin at this dosing schedule in combination with immunotherapy in DLBCL and FL are ongoing,” Dr. Advani concluded.
- Advani RH, Flinn I, Sharman JP, et al. Two doses of polatuzumab vedotin (PoV, anti-CD79b antibody-drug conjugate) in patients (pts) with relapsed/refractory (RR) follicular lymphoma (FL): Durable responses at lower dose level. J Clin Oncol. 2015;33:(suppl; abstr 8503).