A Phase 2 Study of PNT2258 for Treatment of Relapsed or Refractory B-Cell Malignancies.

Background: PNT2258 consists of a native, chemically unmodified, 24-base DNA oligonucleotide designed to target the regulatory region upstream of the BCL2 gene, delivered in a protective liposome. Derangement of BCL2-regulated control mechanisms is a defining characteristic of certain malignancies, and it was hypothesized that the oligonucleotide would promote anticancer activity via suppression of BCL2 transcription.

Methods: PNT2258 was evaluated in this, multicenter, nonrandomized, open-label Phase 2 study in 13 participants with relapsed/refractory B-cell malignancies to investigate potential antitumor activity and safety. Participants with follicular lymphoma, diffuse large B-cell lymphoma, mantle cell lymphoma, or chronic lymphocytic leukemia received intravenous PNT2258 120 mg/m on Days 1 to 5 of a 21-day cycle for up to 8 cycles, followed by 100 mg/m on Days 1 to 2 of a 28-day cycle until study withdrawal.

Results: All 13 participants were treated with PNT2258 monotherapy and evaluable for response and safety and tolerability. The overall response rate was 53.8% (7/13; 95% confidence interval [CI], 25.1%-80.8%). Median duration of response was 23.4 months (range, 3, 31.5). The disease control rate of participants with stable disease or better was 84.6% (95% CI, 54.6%-98.1%). The most frequently (≥50%) observed adverse events (AEs) were nausea, chills, diarrhea, fatigue, headache, vomiting, and back pain. Hypertension (30.8%) and diarrhea (23.1%) were the most frequent grade ≥3 AEs. No deaths were observed.

Conclusion: Clinically meaningful and durable activity with an acceptable safety profile was observed in participants with relapsed/refractory B-cell malignancies who received single-agent PNT2258.

Trial Registration: NCT01733238, first posted 26-Nov-2012. https://clinicaltrials.gov/ct2/show/NCT01733238.