Pembrolizumab ( Keytruda ), an anti–PD-1 antibody, demonstrated antitumor activity and acceptable safety in patients with recurrent or metastatic PD-L1–positive urothelial cancer enrolled in the phase 1b KEYNOTE-012 study.
Researchers have presented updated efficacy and safety data for these patients, as well as an analysis of the relationship between PD-L1 expression and overall response rate ( ORR ).
Eligible patients had recurrent, metastatic, or persistent urothelial cancer of the bladder, renal pelvis, ureter, or urethra.
Patients received Pembrolizumab 10 mg/kg every 2 weeks until complete response, progression, or unacceptable toxicity.
PD-L1 expression was evaluated in baseline tumor samples at a central laboratory.
Patients were enrolled if there were greater than or equal to 1% PD-L1–positive cells in tumor nests or a PD-L1–positive band in stroma by a prototype immunohistochemistry assay.
Samples were also analyzed with the clinical trial immunohistochemistry assay.
Response was evaluated every 8 weeks per RECIST v1.1 by central review.
Thirty-three patients were enrolled ( median age, 70 years; greater than or equal to 3 prior therapies, 33%; visceral or osseous metastases, 66% ).
Median follow-up duration was 13 months ( range, 1-16 ).
Grade 3-4 drug-related adverse events occurred in 5 ( 15% ) patients.
In the 28 patients with measurable disease at baseline, ORR was 25% ( 95% CI 11-45 ), with 3 ( 11% ) complete and 4 ( 14% ) partial responses per central review.
At the time of analysis, median duration of response had not been reached ( range, 16-50+ weeks ). The 12-month progression-free survival rate was 19%.
ORR in patients with tumors positive for PD-L1 expression as assessed with the clinical trial assay was 38%.
In conclusion, Pembrolizumab has demonstrated durable antitumor activity in patients with advanced urothelial cancer.
A higher response rate was seen in patients with PD-L1 expression. ( Xagena )
Source: ASCO Annual Meeting, 2015