Activation of T cells usually requires two signals. Signal 1 is mediated via a peptide-MHC on the APC; signal 2 is mediated via a costimulatory molecule on the APC surface. We demonstrate here that naive CD4+ T cells actually acquire the costimulatory molecule CD80 (B7-1) from syngeneic APCs after activation. This phenomenon was demonstrated showing acquisition of CD80 by T cells from CD80/CD86 (B7-2) knockout mice, and by treating T cells with cyclohexamide to further rule out endogenous expression of CD80 by T cells. Moreover, no CD80 mRNA could be detected in T cells that had acquired CD80. The amount of acquisition of CD80 by T cells was shown to be directly related to both the strength of signal 1 and the amount of CD80 on the APC. Specificity of this acquisition was also shown by the lack of acquisition by T cells from CD28 knockout mice (implicating CD28 in this process), the lack of acquisition of CD40 (another molecule on the APC surface) by T cells, and confocal microscopy studies. We demonstrate for the first time that 1) naive T cells, following acquisition of CD80 from APCs, were themselves shown to be capable of acting as APCs; and 2) memory T cells that have acquired CD80 from APCs undergo apoptosis in the presence of increased levels of signal 1. Thus we demonstrate both immunostimulatory and immunoregulatory functions as a result of CD80 acquisition by different T cell populations.

The relative contributions of the direct and indirect pathways in alloimmune responses have not been fully elucidated. We report a novel murine TCR transgenic system that can simultaneously track the CD4-direct (CD4-d), CD4-indirect (CD4-i), and CD8-direct (CD8-d) pathways after transplantation. Using this system, we have observed a profoundly greater proliferation of CD4-i T cells relative to CD4-d and CD8-d T cells after transplantation. Furthermore, a much larger proportion of CD4-i T cells attain an effector phenotype. We also analyzed endogenous, wild-type T cells using enzyme-linked immunospot analysis. In naive mice, T cells with indirect reactivity were undetectable, but T cells with direct reactivity were abundant. However, 10 days after skin or heterotopic heart transplantation, CD4-i T cells comprised approximately 10% of the CD4+ response. Consistent with increased priming of the CD4-i pathway, we observed that the CD4-i T cells were further enriched in the effector cells migrating to the allograft and in the memory-like T cells persisting after rejection. Thus, priming of the CD4-i pathway is favored after transplantation, allowing a rare population to rapidly become a major component of the CD4+ T cell response in acute allograft rejection. The generalizability of this observation to other models remains to be determined.

On June 15, 2020, the FDA granted accelerated approval to lurbinectedin for the treatment of adult patients with metastatic small cell lung cancer (SCLC) with disease progression on or after platinum-based chemotherapy. Approval was granted on the basis of the clinically meaningful effects on overall response rate (ORR) and duration of response (DOR), and the safety profile observed in a multicenter, open-label, multicohort clinical trial (PM1183-B-005-14, NCT02454972), referred to as Study B-005, in patients with advanced solid tumors. The trial included a cohort of 105 patients with metastatic SCLC who had disease progression on or after platinum-based chemotherapy. The confirmed ORR determined by investigator assessment using RECIST 1.1 in the approved SCLC patient population was 35% [95% confidence interval (CI): 26–45], with a median DOR of 5.3 (95% CI: 4.1–6.4) months. The drug label includes warnings and precautions for myelosuppression, hepatotoxicity, and embryo-fetal toxicity. This is the first drug approved by the FDA in over 20 years in the second line for patients with metastatic SCLC. Importantly, this approval includes an indication for patients who have platinum-resistant disease, representing an area of particular unmet need.

On May 26, 2020, the FDA approved nivolumab with ipilimumab and two cycles of platinum-doublet chemotherapy as first-line treatment for patients with metastatic or recurrent non–small cell lung cancer (NSCLC), with no EGFR or anaplastic lymphoma kinase (ALK) genomic tumor aberrations. The approval was based on results from Study CA2099LA (CheckMate 9LA), an open-label trial in which 719 patients with NSCLC were randomized to receive nivolumab with ipilimumab and two cycles of chemotherapy (n = 361) or four cycles of platinum-doublet chemotherapy (n = 358). Overall survival (OS) was improved for patients who received nivolumab with ipilimumab and chemotherapy, with a median OS of 14.1 months [95% confidence interval (CI), 13.2–16.2] compared with 10.7 months (95% CI, 9.5–12.5) for patients who received chemotherapy (HR, 0.69; 96.71% CI, 0.55–0.87; P = 0.0006). Progression-free survival and overall response rate per blinded independent central review were also statistically significant. This was the first NSCLC application reviewed under FDA's Project Orbis, in collaboration with Singapore's Health Sciences Authority, Australia's Therapeutic Goods Administration, and Health Canada. The benefit–risk analysis supports FDA's approval of nivolumab with ipilimumab and chemotherapy.