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Canine malignant melanoma provides a clinically relevant, large animal parallel patient population to study the GD2-reactive hu14.18-IL-2 immunocytokine as it is similar to human melanoma and expresses GD2. The objectives of this study were to evaluate safety, radiation fractionation, and identify informative biomarkers of an in-situ tumor vaccine involving local radiation therapy plus intratumoral-immunocytokine in melanoma tumor-bearing dogs. Twelve dogs (six dogs/arm) with locally advanced or metastatic melanoma were randomized to receive a single 8 Gy fraction (arm A) or three 8 Gy fractions over 1 week (arm B) to the primary site and regional lymph nodes (when clinically involved) with the single or last fraction 5 days before intratumoral-immunocytokine at 12 mg/m 2 on 3 consecutive days. Serial tumor biopsies were obtained. All 12 dogs completed protocol treatment, and none experienced significant or unexpected adverse events. Evidence of antitumor activity includes one dog with a complete response at day 60, one dog with a partial response at day 60, and four dogs with mixed responses. Histology of serial biopsies shows a variably timed increase in intratumoral lymphocytic inflammation in some dogs. Canine NanoString analyses of serial biopsies identified changes in gene signatures of innate and adaptive cell types versus baseline. There were no significant differences in NanoString results between arm A and arm B. We conclude that intratumoral-immunocytokine in combination with local radiation therapy in canine melanoma is well tolerated and has antitumor activity with the potential to inform clinical development in melanoma patients., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

We report an in situ vaccination, adaptable to nearly any type of cancer, that combines radiotherapy targeting one tumor and intratumoral injection of this site with tumor-specific antibody and interleukin-2 (IL-2; 3xTx). In a phase I clinical trial, administration of 3xTx (with an immunocytokine fusion of tumor-specific antibody and IL-2, hu14.18-IL2) to subjects with metastatic melanoma increases peripheral CD8 + T cell effector polyfunctionality. This suggests the potential for 3xTx to promote antitumor immunity against metastatic tumors. In poorly immunogenic syngeneic murine melanoma or head and neck carcinoma models, 3xTx stimulates CD8 + T cell-mediated antitumor responses at targeted and non-targeted tumors. During 3xTx treatment, natural killer (NK) cells promote CTLA4 + regulatory T cell (T reg ) apoptosis in non-targeted tumors. This is dependent on NK cell expression of CD86, which is upregulated downstream of KLRK1. NK cell depletion increases T reg infiltration, diminishing CD8 + T cell-dependent antitumor response. These findings demonstrate that NK cells sustain and propagate CD8 + T cell immunity following 3xTx., Competing Interests: Declaration of interests Z.S.M. is a member of the scientific advisory boards for Archeus Technologies, NorthStar Medical Isotopes, and Seneca Therapeutics., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Rationale: Murine syngeneic tumor models have revealed efficacious systemic antitumor responses following primary tumor in situ vaccination combined with targeted radionuclide therapy to secondary or metastatic tumors. Here we present studies on the safety and feasibility of this approach in a relevant translational companion dog model (n = 17 dogs) with advanced cancer., Methods: The three component of the combination immuno-radiotherapy approach were employed either separately or in combination in companion dogs with advanced stage cancer. In situ vaccination was achieved through the administration of hypofractionated external beam radiotherapy and intratumoral hu14.18-IL2 fusion immunocytokine injections to the index tumor. In situ vaccination was subsequently combined with targeted radionuclide therapy using a theranostic pairing of IV 86Y-NM600 (for PET imaging and subject-specific dosimetry) and IV 90Y-NM600 (therapeutic radionuclide) prescribed to deliver an immunomodulatory 2 Gy dose to all metastatic sites in companion dogs with metastatic melanoma or osteosarcoma. In a subset of dogs, immunologic parameters preliminarily assessed., Results: The components of the immuno-radiotherapy combination were well tolerated either alone or in combination, resulting in only transient low grade (1 or 2) adverse events with no dose-limiting events observed. In subject-specific dosimetry analyses, we observed 86Y-NM600 tumor:bone marrow absorbed-dose differential uptakes ≥2 in 4 of 5 dogs receiving the combination, which allowed subsequent safe delivery of at least 2 Gy 90Y-NM600 TRT to tumors. NanoString gene expression profiling and immunohistochemistry from pre- and post-treatment biopsy specimens provide evidence of tumor microenvironment immunomodulation by 90Y-NM600 TRT., Conclusions: The combination of external beam radiotherapy, intratumoral immunocytokine, and targeted radionuclide immuno-radiotherapy known to have activity against syngeneic melanoma in murine models is feasible and well tolerated in companion dogs with advanced stage, spontaneously arising melanoma or osteosarcoma and has immunomodulatory potential. Further studies evaluating the dose-dependent immunomodulatory effects of this immuno-radiotherapy combination are currently ongoing., Competing Interests: I have read the journal’s policy and the authors of this manuscript have the following compeXng interests: ZM – Scientific Advisory Board Member and equity options, Archeus Technologies, Scientific Advisory Board Member and equity options, Seneca Therapeutics, Research Material support (reagents) from Bristol-Myers Squibb, AstraZeneca, Nektar Therapeutics, Apeiron Biologics, XRAd Therapeutics. BB and JG has ownership interest in Voximetry Inc (Middleton, WI). MRA - Research collaborations through the University of Wisconsin with Bristol Myers Squibb (Redwood City, CA and Princeton, NJ) and with Apeiron Biologics (Vienna, Austria). JW is a co-founder and CSO of Archeus Technologies, Inc (Madison, WI). This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Phase I testing of the hu14.18-IL2 immunocytokine (IC) in melanoma patients showed immune activation, reversible toxicities, and a maximal tolerated dose of 7.5 mg/m 2 /day. Preclinical data in IC-treated tumor-bearing mice with low tumor burden documented striking antitumor effects. Patients with completely resectable recurrent stage III or stage IV melanoma were scheduled to receive 3 courses of IC at 6 mg/m 2 /day i.v. on days 1, 2 and 3 of each 28-day course. Patients were randomized to complete surgical resection either following neoadjuvant (Group A) or prior to adjuvant (Group B) IC course 1. Primary objectives were to: (1) evaluate histological evidence of anti-tumor activity and (2) evaluate recurrence-free survival (RFS) and OS. Twenty melanoma patients were randomized to Group A (11 patients) or B (9 patients). Two Group B patients did not receive IC due to persistent disease following surgery. Six of 18 IC-treated patients remained free of recurrence, with a median RFS of 5.7 months (95% confidence interval (CI) 1.8-not reached). The 24-month RFS rate was 38.9% (95% CI 17.5-60.0%). The median follow-up of surviving patients was 50.0 months (range: 31.8-70.4). The 24-month OS rate was 65.0% (95% CI 40.3-81.5%). Toxicities were similar to those previously reported. Exploratory tumor-infiltrating lymphocyte (TIL) analyses suggest prognostic value of TILs from Group A patients. Prolonged tumor-free survival was seen in some melanoma patients at high risk for recurrence who were treated with IC.