Search

Chimeric antigen receptor T (CAR-T) cells show remarkable efficacy for some hematological malignancies. However, CAR targets that are expressed at high level and selective to tumors are scarce. Several strategies have been proposed to tackle the on-target off-tumor toxicity of CAR-T cells that arise from suboptimal selectivity, but these are complicated, with many involving dual gene expression for specificity. In this study, we show that switchable CAR-T cells with a tumor targeting adaptor can mitigate on-target off-tumor toxicity against a low selectivity tumor antigen that cannot be targeted by conventional CAR-T cells, such as CD40. Our system is composed of anti-cotinine murine CAR-T cells and cotinine-labeled anti-CD40 single chain variable fragments (scFv), with which we show selective tumor killing while sparing CD40-expressing normal cells including macrophages in a mouse model of lymphoma. Simple replacement of the tumor-targeting adaptor with a suicidal drug-conjugated tag may further enhance safety by enabling permanent in vivo depletion of the switchable CAR-T cells when necessary. In summary, our switchable CAR system can control CAR-T cell toxicity while maintaining therapeutic efficacy, thereby expanding the range of CAR targets. The therapeutic success of CAR-T cells depends on the availability of selective and high-density targets, which limits their applicability due to on-target off-tumor toxicity. Here authors overcome this limitation in a mouse model of immune therapy in which an adaptor is an epitope-tagged single chain variable fragment targeting the tumour antigen, and the CAR-T cells are targeting the epitope, thus enabling a precise dose-switch. [ABSTRACT FROM AUTHOR]

Purpose: Cancers deficient in homologous recombination DNA repair, such as those with BRCA1 or BRCA2 (BRCA1/2) mutations rely on a pathway mediated by the enzyme poly(adenosine diphosphate-ribose) polymerase (PARP). PARP inhibitors (PARPi's) have demonstrated efficacy in treating patients with germline (g)BRCA1/2, somatic (s)BRCA1/2, and gPALB2 mutations in clinical trials. However, patients with a poor performance status (PS) and those with severe organ impairment are often excluded from clinical trials and cancer-directed treatment. Methods: We report the cases of two patients with metastatic breast cancer who had poor PS, significant visceral disease, and gPALB2 and sBRCA mutations, who derived significant clinical benefit from treatment with PARP inhibition. Results: Patient A had germline testing demonstrating a heterozygous PALB2 pathogenic mutation (c.3323delA) and a BRCA2 variant of unknown significance (c.9353T>C), and tumor sequencing revealed PALB2 (c.228_229del and c.3323del) and ESR1 (c.1610A>C) mutations. Patient B was negative for pathologic BRCA mutations upon germline testing, but tumor sequencing demonstrated somatic BRCA2 copy number loss and a PIK3CA mutation (c.1633G>A). Treatment with PARPi's in these two patients with an initial PS of 3–4 and significant visceral disease resulted in prolonged clinical benefit. Conclusion: Patients with a poor PS, such as those described here, may still have meaningful clinical responses to cancer treatments targeting oncogenic drivers. More studies evaluating PARPi's beyond gBRCA1/2 mutations and in sub-optimal PS would help identify patients who may benefit from these therapies. [ABSTRACT FROM AUTHOR]