Pembrolizumab with low-dose carboplatin for recurrent platinum-resistant ovarian, fallopian tube, and primary peritoneal cancer: survival and immune correlates.

BACKGROUND: Anti-programmed death 1 (PD1)/programmed cell death ligand 1 (PD-L1) therapies have shown modest activity as monotherapy in recurrent ovarian cancer. Platinum chemotherapies induce T-cell proliferation and enhance tumor recognition. We assessed activity and safety of pembrolizumab with carboplatin in recurrent platinum-resistant ovarian cancer. PATIENTS AND METHODS: This phase I/II, single-arm clinical trial studied concurrent carboplatin and pembrolizumab in recurrent platinum-resistant ovarian, fallopian tube, and primary peritoneal cancer. Primary platinum refractory patients were excluded. Patients were treated after progression on subsequent non-platinum systemic therapy after becoming platinum resistant or refractory. Pembrolizumab 200 mg was given on day 1 and carboplatin area under the curve 2 on days 8 and 15 of a 3-week cycle until progression. Imaging was assessed by blinded independent review. PD-L1 expression was assessed by immunohistochemistry. Flow cytometry on peripheral blood mononuclear cells was performed for CD3, CD4, CD8, PD1, CTLA4 and Ki67. RESULTS: The most common treatment-related adverse events were lymphopenia (18%) and anemia (9%) with most being grade 1 or 2 (93%). Of 29 patients treated, 23 patients were evaluable for best objective response: 10.3% (95% CI 2.2 to 27.4) had partial response (PR), 51.7% (95% CI 32.5 to 70.6) had stable disease (SD). 56.5% of patients had decreases in target lesions from baseline. All PD-L1-positive patients achieved PR (3/7, 42.8%) or SD (4/7, 57.2%). Median progression-free survival was 4.63 months (95% CI 4.3 to 4.96). Median OS was 11.3 months (95% CI 6.094 to 16.506). Peripheral CD8+PD1+Ki67+ T cells expanded after 3 (p=0.0015) and 5 (p=0.0023) cycles. CTLA4+PD1+CD8+ T cells decreased through the course of treatment up to the 12th cycle (p=0.004). When stratified by ratio of peripheral CD8+PD1+Ki67+ T cells to tumor burden at baseline, patients with a ratio ≥0.0375 who had a significantly longer median OS of 18.37 months compared with those with a ratio <0.0375 who had a median OS of 8.72 months (p=0.0099). No survival advantage was seen with stratification by tumor burden alone (p=0.24) or by CD8+PD1+Ki67+ T cells alone (p=0.53). CONCLUSIONS: Pembrolizumab with carboplatin was well-tolerated and active in recurrent platinum-resistant ovarian cancer. A ratio of peripheral T-cell exhaustion to radiographic tumor burden may identify patients more likely to benefit from this chemoimmunotherapy. TRIAL REGISTRATION NUMBER: NCT03029598.

Phase II trial of albumin-bound paclitaxel and granulocyte macrophage colony-stimulating factor as an immune modulator in recurrent platinum resistant ovarian cancer.

BACKGROUND: Granulocyte macrophage colony-stimulating factor (GM-CSF) stimulates immunity via recruitment of antigen presenting cells and tumor specific T-cell stimulation. Albumin-bound paclitaxel (nab-paclitaxel) followed by GM-CSF may enhance antitumor responses and prolong remissions in ovarian cancer. Immune phenotypes present before treatment may identify responders to chemo-immunotherapy. METHODS: Recurrent platinum-resistant ovarian, peritoneal, or fallopian tube cancer patients received nab-paclitaxel, 100mg/m2 days 1, 8, 15 followed by GM-CSF 250µg days 16-26 every 28days for 6 planned cycles. The primary endpoint was remission duration compared to immediate prior remission. Peripheral blood was evaluated by flow cytometry and interferon-γ ELISPOT. RESULTS: Twenty-one patients were enrolled. Six patients (29%) achieved a biochemical complete response and 9 (43%) a partial response for an overall response rate of 72%. Median time to progression was 4months and 10% of patients achieved longer remissions than the immediate prior regimen. Median overall survival (OS) was 16.8months. Fewer myeloid derived suppressor cells (MDSC) at enrollment significantly associated with complete response (p=0.05). T-cell responses to IGF1R-p1332-1346 (r=0.827, p=0.0003) and IGF1R-p1242-1256 (r=0.850, p=0.0001) during treatment correlated with time to progression. CONCLUSIONS: Nab-paclitaxel combined with GM-CSF demonstrated biochemical responses in a majority of patients, although responses were not sustained. This combination did not demonstrate an advantage in OS over prior studies of nab-paclitaxel monotherapy. Agents that modulate MDSC should be studied as potential adjuvants to therapy. Strategies to expand T cells recognizing tumor-associated antigens biologically significant in ovarian cancer should also continue to be investigated.