Clinical outcomes in colorectal cancer (CRC) correlate with T cell infiltrates, but the specific contributions of heterogenous T cell types remain unclear. To investigate the diverse function of T cells in CRC, we profiled 37,931 T cells from tumors and adjacent normal colon of 16 patients with CRC with respect to transcriptome, TCR sequence, and cell surface markers. Our analysis identified phenotypically and functionally distinguishable effector T cell types. We employed single-cell gene signatures from these T cell subsets to query the TCGA database to assess their prognostic significance. We found 2 distinct cytotoxic T cell types. GZMK ⁺ KLRG1 ⁺ cytotoxic T cells were enriched in CRC patients with good outcomes. GNLY ⁺ CD103 ⁺ cytotoxic T cells with a dysfunctional phenotype were not associated with good outcomes, despite coexpression of CD39 and CD103, markers that denote tumor reactivity. We found 2 distinct Treg subtypes associated with opposite outcomes. While total Tregs were associated with good outcomes, CD38 ⁺ Tregs were associated with bad outcomes independently of stage and possessed a highly suppressive phenotype, suggesting that they inhibit antitumor immunity in CRC. These findings highlight the potential utility of these subpopulations in predicting outcomes and support the potential for novel therapies directed at CD38 ⁺ Tregs or CD8 ⁺ CD103 ⁺ T cells.

Purpose: We report results from two clinical trials of the cyclic dinucleotide stimulator of IFN genes (STING) agonist ulevostinag. Patients and Methods: In a phase I study (NCT03010176) with an accelerated titration design/modified toxicity probability interval method, participants with advanced/metastatic solid tumors or lymphomas received intratumoral ulevostinag (±intravenous pembrolizumab). In an expansion phase, participants with head and neck squamous cell carcinoma (HNSCC) or triple-negative breast cancer received the combination. Primary objectives were safety/tolerability and identifying the recommended phase II dose; biomarkers were exploratory. In a randomized phase II study (NCT04220866), participants with untreated metastatic or unresectable, recurrent HNSCC received intravenous pembrolizumab (±ulevostinag 540 µg). The primary objective was antitumor activity. Pembrolizumab 200 mg was administered every 3 weeks in both studies. Results: In the phase I study (NCT03010176; N = 156), the most common adverse event was pyrexia (70%). Plasma ulevostinag concentrations increased dose-dependently. Circulating levels of C-X-C motif chemokine 10, IFNγ, and IL-6 showed elevation at 2 to 4 hours, peak at 6 to 8 hours, and plateau/partial resolution at 24 hours but, beyond the 540 µg dose, did not show a clear dose–effect relationship. Ten participants experienced dose-limiting toxicities; the recommended phase II dose for intratumoral ulevostinag was 540 µg. In the phase II study (NCT04220866), 4 of 8 participants treated with combination therapy and 1 of 10 treated with pembrolizumab monotherapy had a complete or partial response. The most common adverse event was pyrexia (n = 5). Conclusions: Intratumoral ulevostinag (±pembrolizumab) had manageable toxicity, dose-dependent pharmacokinetics, and evidence of STING activation and target engagement. Combination therapy showed antitumor activity in participants with untreated metastatic or unresectable, recurrent HNSCC.

PURPOSE: Uterine leiomyosarcoma (uLMS) is an aggressive subtype of soft-tissue sarcoma with frequent metastatic relapse after curative surgery. Chemotherapy provides limited benefit for advanced disease. Multiomics profiling studies have identified homologous recombination deficiency in uLMS. In preclinical studies where olaparib and temozolomide provided modest activity, the combination was highly effective for inhibiting uLMS tumor growth. PATIENTS AND METHODS: NCI Protocol 10250 is a single-arm, open-label, multicenter, phase II study evaluating olaparib and temozolomide in advanced uLMS. Patients with progression on ≥1 prior line received temozolomide 75 mg/m² orally once daily with olaparib 200 mg orally twice a day both on days 1-7 in 21-day cycles. The primary end point was the best objective response rate (ORR) within 6 months. A one-stage binomial design was used. If ≥5 of 22 responded, the treatment would be considered promising (93% power; α = .06). All patients underwent paired biopsies that were evaluated with whole-exome sequencing (WES)/RNAseq and a RAD51 foci formation assay. RESULTS: Twenty-two patients were evaluable. The median age was 55 years, and 59% had received three or more prior lines. Best ORR within 6 months was 23% (5 of 22). The overall ORR was 27% (6 of 22). The median progression-free survival (mPFS) was 6.9 months (95% CI, 5.4 months to not estimable). Hematologic toxicity was common (grade 3/4 neutropenia: 75%; thrombocytopenia: 32%) but manageable with dose modification. Five of 16 (31%) of tumors contained a deleterious homologous recombination gene alteration by WES, and 9 of 18 (50%) were homologous recombination-deficient by the RAD51 assay. In an exploratory analysis, mPFS was prolonged for patients with homologous recombination-deficient versus homologous recombination-proficient tumors (11.2 v 5.4 months, P = .05) by RAD51. CONCLUSION: Olaparib and temozolomide met the prespecified primary end point and provided meaningful clinical benefit in patients with advanced, pretreated uLMS.

Sarcoma is a rare cancer arising from soft tissue and bone and consists of more than 50 distinct subtypes. There is an increasing emphasis on understanding the cancer biology of individual sarcoma subtypes to inform the development of targeted and immunotherapy-based treatment approaches. While some advances have recently been made in this respect, most sarcomas are still treated with chemotherapy. The homologous recombination DNA repair pathway plays an important role in repairing highly cytotoxic double-stranded DNA breaks and restarting stalled replication forks. A subset of human cancers, notably ovarian, breast, prostate, and pancreatic cancers, harbor defects in components of the homologous recombination repair pathway, such as mutation or loss of BRCA1/2, and are sensitive to treatments which induce double stranded DNA breaks or replication fork arrest, including oral small molecule poly-ADP-ribose polymerase (PARP) inhibitors. Our understanding of DNA repair defects in sarcoma remains at an early stage. Recently, uterine leiomyosarcoma was identified as a sarcoma subtype with characteristic defects in the homologous recombination repair pathway and frequent BRCA2 loss. Preclinical data, presented here, demonstrates marked activity for the PARP inhibitor olaparib in combination with the alkylating agent temozolomide in leiomyosarcoma models. Ongoing research promises to identify other sarcomas with DNA repair defects and may offer a new opportunity for the targeted treatment of this rare, aggressive cancer.

As leiomyosarcoma patients are challenged by the development of metastatic disease, effective systemic therapies are the cornerstone of outcome. However, the overall activity of the currently available conventional systemic treatments and the prognosis of patients with advanced or metastatic disease are still poor, making the treatment of this patient group challenging. Therefore, in a joint effort together with patient networks and organizations, namely Sarcoma Patients EuroNet (SPAEN), the international network of sarcoma patients organizations, and the National LeioMyoSarcoma Foundation (NLMSF) in the United States, we aim to summarize state-of-the-art treatments for leiomyosarcoma patients in order to identify knowledge gaps and current unmet needs, thereby guiding the community to design innovative clinical trials and basic research and close these research gaps. This position paper arose from a leiomyosarcoma research meeting in October 2020 hosted by the NLMSF and SPAEN.

Purpose: To evaluate sitravatinib, an inhibitor of multiple receptor tyrosine kinases (RTK), for the treatment of well-differentiated/dedifferentiated liposarcoma (WD/DD LPS). Patients and Methods: This multicenter, open-label, Phase II trial enrolled patients with advanced WD/DD LPS who had received at least one prior systemic regimen and had progression within 12 weeks of enrollment. Patients received sitravatinib 150 mg (later amended to 120 mg) orally daily. A Simon two-stage design was used to evaluate for an improvement in the primary endpoint, progression-free rate at 12 weeks (PFR12), from 20% to 40%. Secondary endpoints included antitumor activity and safety. A subset of patients underwent paired biopsies analyzed using reverse-phase protein array. Results: Twenty-nine patients enrolled. Median age was 62 years and 31% had received 3 or more prior lines. Most patients (93%) had DDLPS or mixed WD/DD LPS. Overall, 12 of 29 patients (41%) were alive and progression-free at 12 weeks and the study met the primary endpoint. There were no confirmed responses. Median progression-free survival was 11.7 weeks [95% confidence interval (CI): 5.9–35.9] and median overall survival was 31.7 weeks (95% CI: 18.1–90.1). The most common treatment-related adverse events were diarrhea (59%), hypertension (52%), hoarseness (41%), mucositis (31%), and nausea (31%). Baseline expression of phospho-RTKs was not significantly different between patients with and without clinical benefit from sitravatinib, but the number of samples was small. Conclusions: Sitravatinib provided a PFR12 of 41% and meaningful disease control in a subset of patients with advanced, progressive WD/DD LPS.