Sir Peter MacCallum Department of Oncology - Research Publications
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ItemNo Preview AvailablePreclinical Evidence of the Efficacy of Lewis Y Car T Cells in Patient-Derived Models of Prostate Cancer(The Endocrine Society, 2021-05-03)Abstract Chimeric antigen receptor T (CAR T) cell therapy is an adoptive immunotherapy that has led to new treatments for lymphoma, leukemia, and other blood cancers; however, its efficacy for prostate cancer remains unproven. Here we report pre-clinical evidence of the efficacy of CAR T cell therapy against the Lewis Y antigen (LeY) using patient-derived models of prostate cancer. To assess the expression of LeY on prostate tumours, we performed immunohistochemistry on a cohort of 41 patient-derived xenografts (PDXs). Cytoplasmic and membrane expression were separately assessed and quantified, for each patient. Overall, 61% (25/41) of PDXs were positive for membrane LeY expression, of which 18 PDXs had greater than 50% membrane-positive cells, and considered most suitable to detection and stable binding by anti-LeY CAR T’s. To determine the in vitro sensitivity to CAR T cytotoxicity, we selected 4 PDXs with high and 2 PDXs with low LeY expression using 3 androgen receptor (AR)-positive adenocarcinomas and 3 AR-negative tumors expressing neuroendocrine markers. Next we established organoids for in vitro co-culture assays where organoids were co-incubated with an equal number of anti-LeY+ CAR T cells or Empty vector control CAR T cells (Ev CAR T). Using time-lapse microscopy we reported destruction of organoids by LeY+ CAR T cells as indicated by their morphological collapse and uptake of propidium iodide from the culture medium; control Ev CAR T cells produced no cytotoxicity. Over the 48h assay, the level of target cell death of the LeY+ organoids was correlated to the intensity LeY surface expression. Target cell death mediated by the CAR T cells required perforin and granzyme B, as potent and highly specific small molecule inhibitors of perforin (SN34960) and granzyme B (C20) applied alone or in combination greatly decreased PI uptake, indicating organoid survival. Neither inhibitor adversely affected CAR T cell viability as measured by PI and Annexin V staining. This demonstrated canonical activation of granule exocytosis pathway by the CAR T cells, leading to organoid cell death. To assess CAR T cell efficacy in vivo, we selected one PDX with high LeY expression. Monotherapy with CAR T cells failed to decrease tumour volume compared to vehicle control. However, CAR T cells given after a single dose of the chemotherapeutic agent carboplatin greatly and durably reduced tumour burden, with residual tumour mass being less than 1% of their original size (0.56 ± 0.23% of tumour volume at the start of treatment). Overall, these data provide preclinical evidence that: i) high membrane expression of LeY correlates with in vitro and in vivo CAR T cell-induced tumour cell death via the canonical perforin/granzyme B mechanism; and, ii) membrane LeY can be used as a biomarker for patient selection.
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ItemA phase I/II study of stereotactic radiotherapy and pembrolizumab for oligometastatic renal tumours (RAPPORT): Clinical trial protocol(ELSEVIER INC, 2021-03)BACKGROUND: The management of oligometastatic clear cell renal cell carcinoma (ccRCC) varies widely, ranging from observation to resection or systemic therapies. Prolonged survival has been observed following resection or stereotactic ablative body radiotherapy (SABR). Immunotherapy combinations have shown survival benefits, however, toxicity is higher than that for monotherapy and complete response rates remain less than 10%. The combination of effective local therapies in conjunction with immunotherapy may provide more durable control and pre-clinical models have suggested a synergistic immune-priming effect of SABR. OBJECTIVES: and Methods: RAPPORT is a prospective, single arm, phase I/II study assessing the safety, efficacy and biological effects of single fraction SABR followed by pembrolizumab for oligometastatic ccRCC. The study will include 30 patients with histological confirmed ccRCC and 1-5 oligometastases, one or more of which must be suitable for SABR. Patients can have received prior systemic therapy but not prior immunotherapy. A single 20Gy of SABR is followed 5 days later by 8 cycles of 200 mg pembrolizumab, every 3 weeks. Adverse events are recorded using CTCAE V4.03 and tumour response evaluated by Response Evaluation Criteria in Solid Tumours version 1.1 (RECIST 1.1). Tumour tissue and peripheral blood samples will be collected pre-, during and post-treatment to assess longitudinal changes in immune subsets. OUTCOMES AND SIGNIFICANCE: The RAPPORT study will provide important safety and early efficacy data on the combination of SABR and pembrolizumab in oligometastatic ccRCC and will provide an insight into the underlying biological effects of combination therapy. TRIAL REGISTRATION: clinicaltrials.gov ID NCT02855203.