BACKGROUND Alterations in hedgehog signaling are implicated in the pathogenesis of basal-cell carcinoma. Although most basal-cell carcinomas are treated surgically, no effective therapy exists for locally advanced or metastatic basal-cell carcinoma. A phase 1 study of vismodegib (GDC-0449), a first-in-class, small-molecule inhibitor of the hedgehog pathway, showed a 58% response rate among patients with advanced basal-cell carcinoma. METHODS In this multicenter, international, two-cohort, nonrandomized study, we enrolled patients with metastatic basal-cell carcinoma and those with locally advanced basal-cell carcinoma who had inoperable disease or for whom surgery was inappropriate (because of multiple recurrences and a low likelihood of surgical cure, or substantial anticipated disfigurement). All patients received 150 mg of oral vismodegib daily. The primary end point was the independently assessed objective response rate; the primary hypotheses were that the response rate would be greater than 20% for patients with locally advanced basal-cell carcinoma and greater than 10% for those with metastatic basal-cell carcinoma. RESULTS In 33 patients with metastatic basal-cell carcinoma, the independently assessed response rate was 30% (95% confidence interval [CI], 16 to 48; P = 0.001). In 63 patients with locally advanced basal-cell carcinoma, the independently assessed response rate was 43% (95% CI, 31 to 56; P<0.001), with complete responses in 13 patients (21%). The median duration of response was 7.6 months in both cohorts. Adverse events occurring in more than 30% of patients were muscle spasms, alopecia, dysgeusia (taste disturbance), weight loss, and fatigue. Serious adverse events were reported in 25% of patients; seven deaths due to adverse events were noted. CONCLUSIONS Vismodegib is associated with tumor responses in patients with locally advanced or metastatic basal-cell carcinoma. (Funded by Genentech; Erivance BCC ClinicalTrials.gov number, NCT00833417.)

Among patients with advanced cutaneous squamous-cell carcinoma, cemiplimab induced a response in approximately half the patients and was associated with adverse events that usually occur with immune checkpoint inhibitors. (Funded by Regeneron Pharmaceuticals and Sanofi; ClinicalTrials.gov numbers, NCT02383212 and NCT02760498 .).

Immunotherapies that block inhibitory checkpoint receptors on T cells have transformed the clinical care of cancer patients 1 . However, whether the T cell response to checkpoint blockade relies on reinvigoration of pre-existing tumor infiltrating T cells (TILs) or on recruitment of novel T cells remains unclear 2 – 4 . Here, we performed paired single-cell RNA (scRNA) and T cell receptor (TCR)- sequencing on 79,046 cells from site-matched tumors from patients with basal cell carcinoma (BCC) or squamous cell carcinoma (SCC) pre- and post-anti-PD-1 therapy. Tracking TCR clones and transcriptional phenotypes revealed a coupling of tumor-recognition, clonal expansion, and T cell dysfunction marked by clonal expansions of CD8 + CD39 + T cells, which co-expressed markers of chronic T cell activation and exhaustion. However, this expansion did not derive from pre-existing TIL clones; rather, it was comprised of novel clonotypes not previously observed in the same tumor. Clonal replacement of T cells was preferentially observed in exhausted CD8 + T cells and evident in BCC and SCC patients. These results demonstrate that pre-existing tumor-specific T cells may have limited reinvigoration capacity, and that the T cell response to checkpoint blockade derives from a distinct repertoire of T cell clones that may have just recently entered the tumor.

Understanding complex tissues requires single-cell deconstruction of gene regulation with precision and scale. Here, we assess the performance of a massively parallel droplet-based method Reprints and permissions information is available at www.nature.com/reprints.

Summary Advanced basal cell carcinomas (BCCs) frequently acquire resistance to Smoothened (SMO) inhibitors through unknown mechanisms. Here, we identify SMO mutations in 50% (22/44) of resistant BCCs and show that these mutations maintain Hedgehog signaling in the presence of SMO inhibitors. Alterations include four ligand binding pocket mutations defining sites of inhibitor binding and four variants confering constitutive activity and inhibitor resistance, illuminating pivotal residues that ensure receptor autoinhibition. In the presence of a SMO inhibitor, tumor cells containing either class of SMO mutants effectively outcompete cells containing the wild type SMO. Finally, we show that both classes of SMO variants respond to aPKC-ι/λ or GLI2 inhibitors that operate downstream of SMO, setting the stage for the clinical use of GLI antagonists.