Background The results of phase 1 and phase 2 studies suggest that nivolumab (a PD-1 checkpoint inhibitor) and ipilimumab (a CTLA-4 checkpoint inhibitor) have complementary activity in metastatic melanoma. In this randomized, double-blind, phase 3 study, nivolumab alone or nivolumab combined with ipilimumab versus ipilimumab alone were evaluated in patients with metastatic melanoma. Methods We randomly assigned 945 previously untreated patients with unresectable stage III or IV melanoma, in 1:1:1 ratio, to nivolumab alone (3 mg per kilogram of body weight every 2 weeks), or to nivolumab (at a dose of 1 mg per kilogram) plus ipilimumab (at a dose of 3 mg per kilogram) every 3 weeks for 4 doses followed by nivolumab (3 mg per kilogram every 2 weeks), or to ipilimumab alone (3 mg per kilogram every 3 weeks for 4 doses). Progression-free and overall survival were co-primary end points. Patients continue to be followed for overall survival. Results Median progression-free survival was 11.5 months (95% confidence interval [CI], 8.9 to 16.7) for nivolumab plus ipilimumab as compared with 2.9 months (95% CI, 2.8 to 3.4) for ipilimumab alone (hazard ratio, 0.42; 95% CI, 0.31 to 0.57; P<0.00001), and was 6.9 months (95% CI, 4.3 to 9.5) for nivolumab alone (hazard ratio in the comparison with ipilimumab alone, 0.57; 95% CI, 0.43 to 0.76; P<0.00001). In PD-L1-positive patients, median progression-free survival was 14.0 months in both the nivolumab plus ipilimumab and nivolumab alone groups, but in PD-L1-negative patients, progression-free survival was longer with the combination as compared with nivolumab alone (11.2 months [95% CI, 8.0 to not reached] versus 5.3 months [95% CI, 2.8 to 7.1]). Grade 3–4 drug-related adverse events occurred in 16.3%, 55.0%, and 27.3% of patients in the nivolumab, nivolumab plus ipilimumab, and ipilimumab alone groups, with 1, 0, and 1 drug-related deaths, respectively. Conclusions Nivolumab alone or combined with ipilimumab significantly improved progression-free survival, as compared with ipilimumab, among previously untreated patients with metastatic melanoma. Results with the combination versus either agent alone suggest complementary activity between PD-1 and CTLA-4 blockade, particularly for patients with PD-L1-negative tumors. (Funded by Bristol-Myers Squibb; CheckMate 067, ClinicalTrials.gov number, NCT01844505.)

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Summary The abscopal effect is a phenomenon in which local radiotherapy is associated with the regression of metastatic cancer at a distance from the irradiated site. The abscopal effect may be mediated by activation of the immune system. Ipilimumab is a monoclonal antibody that inhibits an immunologic checkpoint on T cells, cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4). We report a case of the abscopal effect in a patient with melanoma treated with ipilimumab and radiotherapy. Temporal associations were noted: tumor shrinkage with antibody responses to the cancer–testis antigen NY-ESO-1, changes in peripheral-blood immune cells, and increases in antibody responses to other antigens after radiotherapy. (Funded by the National Institutes of Health and others.)

Human embryonic stem (huES) cells have the ability to differentiate into a variety of cell lineages and potentially provide a source of differentiated cells for many therapeutic uses. However, little is known about the mechanism of differentiation of huES cells and factors regulating cell development. We have used high-quality microarrays containing 16 659 seventy-base pair oligonucleotides to examine gene expression in 6 of the 11 available huES cell lines. Expression was compared against pooled RNA from multiple tissues (universal RNA) and genes enriched in huES cells were identified. All 6 cell lines expressed multiple markers of the undifferentiated state and shared significant homology in gene expression (overall similarity coefficient > 0.85). A common subset of 92 genes was identified that included Nanog, GTCM-1, connexin 43 (GJA1), oct-4, and TDGF1 (cripto). Gene expression was confirmed by a variety of techniques including comparison with databases, reverse transcriptase-polymerase chain reaction, focused cDNA microarrays, and immunocytochemistry. Comparison with published "stemness" genes revealed a limited overlap, suggesting little similarity with other stem cell populations. Several novel ES cell-specific expressed sequence tags were identified and mapped to the human genome. These results represent the first detailed characterization of undifferentiated huES cells and provide a unique set of markers to profile and better understand the biology of huES