Background Immunotherapy targeting the PD-1 axis has activity in several tumor types. We aimed to determine the efficacy and safety of pembrolizumab in patients with untreated brain metastases. Here we present results from a Phase II trial of the PD-1 inhibitor pembrolizumab in patients with new or progressive brain metastases from melanoma or non-small cell lung cancer (NSCLC). Methods Thirty-six patients were enrolled, 18 with melanoma and 18 with NSCLC. Patients had at least one untreated or progressive brain metastasis between 5 and 20 mm in longest diameter without associated neurologic symptoms or the need for corticosteroids. NSCLC patients had tumor tissue demonstrating PD-L1 expression. Patients were treated with pembrolizumab 10 mg/kg every two weeks until progression, and brain metastasis response was assessed every eight weeks by modified RECIST. The primary endpoint was brain metastasis response rate and the analysis was performed on an intent-to-treat basis. The trial is ongoing and here we present an early analysis. The study is registered with clinicaltrials.gov, number NCT02085070. Findings Brain metastasis response rate was 22% and 33% among patients with melanoma and NSCLC, respectively. Responses were durable, with all but one patient who responded demonstrating an ongoing response at the time of data analysis. Treatment-related serious and grade 3–4 adverse events were rare and included transaminitis, colitis, pneumonitis, fatigue, endocrine abnormalities, and acute kidney injury (1 patient each). Serious neurological adverse events included cognitive dysfunction and seizures (1 and 3 patients, respectively), due to pembrolizumab, metastases or both. Interpretation Pembrolizumab demonstrates activity in brain metastases in patients with melanoma or NSCLC with an acceptable safety profile, indicating that there may be a role for systemic immunotherapy in patients with untreated or progressive brain metastases. Funding Merck and the Yale Cancer Center.

Background: We performed a phase II trial of pembrolizumab in patients with NSCLC or melanoma with untreated brain metastases to determine the activity of PD-1 blockade in the CNS. Interim results were previously published, and we now report an updated analysis of the full NSCLC cohort. Methods: This was an open-label, single-institution, phase 2 study. Eligible patients were ≥ 18 years of age with advanced NSCLC with ≥1 brain metastasis 5-20mm not previously treated or progressing after prior radiation, no neurologic symptoms or corticosteroid requirement, and performance status <2. Patients were treated with pembrolizumab 10 mg/kg IV every 2 weeks. Cohort 1 was for patients with PD-L1 ≥1% and cohort 2 PD-L1 <1% or unevaluable. The primary endpoint was the proportion of patients achieving a brain metastasis response. All treated patients were analyzed for response and safety endpoints. This study is closed to accrual and is registered with Clinicaltrials.gov, number NCT02085070. Here we report the updated results of the NSCLC cohort. Findings: Between March 31, 2014 and May 21, 2018, 42 patients were treated. Median followup was 8.3 months (IQR 4.5 to 26.2 months). Eleven of 37 patients in cohort 1 had a brain metastasis response (29.7% [95% CI, 15•9-47•0%]). There were no responses in cohort 2. Grade 3-4 AEs related to treatment included 2 patients with pneumonitis, and 1 each with constitutional symptoms, colitis, adrenal insufficiency, hyperglycemia, and hypokalemia. Treatment-related serious adverse events occurred in 6 (14%) patients and included pneumonitis acute kidney injury, colitis, hypokalemia, and adrenal insufficiency. There were no treatment-related deaths. Interpretation: Pembrolizumab has activity in brain metastases from NSCLC with PD-L1 expression ≥1% and is safe in select patients with untreated brain metastases. Further investigation of immunotherapy in patients with CNS disease from NSCLC is warranted.

Purpose Pembrolizumab is active in melanoma, but activity in patients with untreated brain metastasis is less established. We present long-term follow-up of pembrolizumab-treated patients with new or progressing brain metastases treated on a phase II clinical trial ( ClinicalTrials.gov identifier: NCT02085070). Patients and Methods We enrolled 23 patients with melanoma with one or more asymptomatic, untreated 5- to 20-mm brain metastasis not requiring corticosteroids; 70% of patients had prior systemic therapy. Pembrolizumab was administered for up to 24 months. Brain metastasis response, the primary end point, was assessed by modified Response Evaluation Criteria in Solid Tumors (RECIST). Pretreatment tumors were analyzed for T-cell infiltrate and programmed death ligand 1. Results Six patients (26%) had a brain metastasis response. Eight patients (35%) did not reach a protocol evaluation scan and were unevaluable for brain metastasis response as a result of progression or need for radiation. Brain metastasis and systemic responses were concordant, with all ongoing at 24 months. The median progression-free and overall survival times were 2 and 17 months, respectively. Eleven patients (48%) were alive at 24 months. This included three unevaluable patients. One of these three patients had hemorrhaged, and two had symptoms from perilesional edema requiring radiosurgery, but all three patients remained on commercial pembrolizumab more than 24 months later. None of the 24-month survivors received subsequent BRAF inhibitors. Neurologic adverse events occurred in 65% of patients; all adverse events but one were grade 1 or 2. Three patients had seizures, which were treated with anticonvulsants. Most responders had higher pretreatment tumor CD8 cell density and programmed death ligand 1 expression, whereas all nonresponders did not. Conclusion Pembrolizumab is active in melanoma brain metastases with acceptable toxicity and durable responses. Multidisciplinary care is required to optimally manage patients with brain metastases, including consideration of radiation to large or symptomatic lesions, which were excluded in this trial. Two-year survival was similar to patients without brain metastasis treated with anti–programmed cell death 1 agents. Concordant brain and extracerebral responses support use of pembrolizumab to treat small, asymptomatic brain metastases.