Pembrolizumab shows promise in treatment-refractory prostate cancer

  • Antonarakis ES & al.
  • J Clin Oncol
  • 27 Nov 2019

  • curated by Deepa Koli
  • Univadis Clinical Summaries
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Takeaway

  • Pembrolizumab monotherapy was well tolerated and shows activity in a subset of patients with bone-predominant metastatic castration-resistant prostate cancer (mCRPC) previously treated with docetaxel+targeted endocrine therapy.

Why this matters

  • Promising OS estimates indicate that pembrolizumab may extend survival in these difficult-to-treat patients.

Study design

  • Phase 2 KEYNOTE-199 study of 199 patients with mCRPC previously treated with docetaxel and ≥1 targeted endocrine therapy who received pembrolizumab.
  • Primary endpoint: objective response rate (ORR).
  • Funding: MSD.

Key results

  • 133 patients had PD-L1-positive disease (group 1), 66 had PD-L1-negative disease (group 2), and 59 had bone predominant disease regardless of PD-L1 expression (group 3).
  • In groups 1 and 2:
    • ORR was 5% (95% CI, 2%-11%) and 3% (95% CI,
    • Median duration of response was not reached (range, 1.9 to ≥21.8 months) and 10.6 (range, 4.4-16.8) months, respectively.
  • In groups 1, 2, and 3:
    • Disease control rate was 10%, 9%, and 22%, respectively.
    • Median PFS was 2.1, 2.1, and 3.7 months, respectively.
    • Median OS was 9.5, 7.9, and 14.1 months, respectively.
    • 60% of patients experienced treatment-related adverse events (TEAEs); grade 3-5 TEAEs occurred in 15% of patients.
  • TEAE-related discontinuation rate was 5%.

Limitations

  • No randomization.
  • Open-label design.