Georgina Long, BSc, PhD, MBBS
A treatment regimen of pembrolizumab (Keytruda) plus low-dose ipilimumab (Yervoy) was tolerable and effective for patients with advanced melanoma, with an overall response rate (ORR) of 56%, according to results from the phase Ib KEYNOTE-029 clinical trial.
The rate of grade 3/4 adverse events (AEs) with the combination was 36%, with a 54% incidence of immune-mediated AEs. These findings were similar to what has been seen with other trials exploring the combination of PD-1 and CTLA-4 inhibition, said lead investigator Georgina Long, BSc, PhD, MBBS, medical oncologist at the Melanoma Institute, Australia, during the late-breaking abstract session at the 2015 Society for Melanoma Research Congress.
The KEYNOTE-029 trial included 72 patients with advanced melanoma followed for 18 weeks. Patients were treated in the United States, New Zealand, or Australia with pembrolizumab at 2 mg/kg and four doses of ipilimumab at 1 mg/kg. Nine of the patients in the study (12%) had been previously treated, but none had been treated with checkpoint inhibitor therapies, said Long.
Most of the patients in the KEYNOTE-029 study were male with a median age of 60 years, and 86% were PD-L1 positive. Only 28% of the patients had BRAF
V600 mutations. Eighty five percent of patients had a good ECOG performance status of 0, and only 21% had elevated LDH levels.
Among treatment-naïve patients (n = 63), the ORR was 57%. Among those who had been previously treated, the ORR was 44%. The disease control rate (ORR plus stable disease) was 79%, noted Long. “Only 14 patients in the study, or 19%, were diagnosed with progressive disease,” she said.
The complete response rate was 4% across the full study. There were no complete responses in those who had undergone previous therapy, said Long.
Thirty-seven patients (51%) had a partial response to treatment. The partial response rates were 52% and 44% in the treatment-naïve and pretreated groups, respectively. Stable disease occurred after treatment in 24% of patients.
Altogether, 72% of the patients received all 4 ipilimumab doses, and only 31% discontinued both treatments before the end of the trial. Most of the discontinuations were due to progression (19%) or AEs (10%), said Long.
“The majority of patients with ongoing adverse events experience thyroid-related side effects,” Long said. Ninety three percent of patients experienced treatment-related AEs, but only 22% were rated as “serious” by the investigators. None led to death. Seventeen percent of AEs led to ipilimumab discontinuation before the end of the trial, and 8% of AEs led patients to discontinue both drugs.
The most frequent AE in the KEYNOTE-029 study was rash, which affected 53% of patients. Thirty one percent of patients experienced fatigue and 28% were diagnosed with pruritis during treatment. Seventeen percent of patients experienced hypothyroidism as a result of treatment.
Grade 3 or 4 immune-mediated AEs affected 17% of patients. The most frequent immune-mediated AEs were hypothyroidism, hypophysitis, and hyperthyroidism. Other common immune-mediated AEs were pneumonitis and colitis, Long noted.
“Hypophysitis was more common in this trial than we’ve seen in similar studies, but it’s difficult to say why that occurred,” Long said. “We were very aware of this side effect during the study, and so that may be one explanation."
The KEYNOTE-029 phase Ib trial was a continuation of a smaller clinical study with the same study medications at the same dosages. Enrollment in the earlier study also included patients with renal cell cancer, said Long. Since only 6 patients in the earlier study experienced dose-limiting toxicity, the trial was expanded to 72 patients—all with advanced melanoma.
The investigators will continue to evaluate the efficacy and safety data resulting from the treatment regimen used in the KEYNOTE-029 trial, noted Long. They plan to analyze these outcomes and correlate them with tumor biomarkers, using an expanded data set of 153 patients, she added.
Long G. KEYNOTE-029: Pembolizumab (pembro) + low-dose ipilimumab (ipi) for advanced melanoma. Presented at the Society for Melanoma Research 2015 Congress; November 18-21, 2015; San Francisco, CA.
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