A Novel Melanoma Vaccine Based on a Shared Neoantigen and a Liquid Polymer Platform

摘要 尽管免疫检查点抑制剂和靶向治疗的结果有了显著的改善， 大多数转移性BRAF突变黑色素瘤患者最终会经历疾病的进展。一 抵抗免疫检查点抑制剂的关键原因是黑色素瘤特异性T细胞的缺乏，但 不幸的是，大多数旨在扩增黑色素瘤特异性T细胞的早期黑色素瘤疫苗都失败了 来证明自己的利益。下一代测序和多肽-人类白细胞抗原结合预测已成为可能 研究人员为癌症患者接种新抗原疫苗--新抗原是任何正常人都不表达的多肽 组织，但只在肿瘤中发现。尽管新抗原疫苗前景看好，但一个关键的限制是 新抗原通常是私有的，因此不可能制造出“现成”的新抗原疫苗 这对一大群患者来说是合适的。我们和其他人发现黑色素瘤患者可以 建立内源性T细胞对突变的BRAF的反应(第600位的缬氨酸为谷氨酸)。我们有 进一步证明了一种与人类白细胞抗原A2结合的突变BRAF多肽(MBRAFp)在人类白细胞抗原中具有高度的免疫原性。 A2转基因小鼠。在此，我们提出了针对V600E突变的BRAF的免疫原性疫苗。 人类白细胞抗原A2具有扩增黑色素瘤特异性T细胞的潜力。作为一种共有的新抗原，mBRAFp 大约20%-25%的黑色素瘤患者(40%-50%的黑色素瘤患者)的相关肿瘤靶点 携带BRAF V600E x 50%携带人类白细胞抗原A2的患者)。这种现成的治疗性疫苗可能会用于 作为高危黑色素瘤切除患者或肿瘤负担最小的患者的单一疗法。它也可能是 联合抗PD-1治疗免疫检查点抑制剂治疗无效的黑色素瘤 和靶向治疗。我们的疫苗由mBRAFp和Resiquimod(RSQ)作为佐剂组成，配方为 CAPRO™-一种新型专利可生物降解液体聚合物，可提供两种药物的局部控制释放 抗原和佐剂。先前我们发现(1)用卵清蛋白(OVA)和RSQ免疫的小鼠 在CAPRO中产生了持久的OVA特异性抗体和CD8 T细胞反应，以及(2)CAPRO负载 MBRAFp和RSQ在人类白细胞抗原A2转基因小鼠中诱导抗原特异性T细胞反应。基于这些 令人满意的结果是，我们已经启动了涉及疫苗CMC的临床前产品开发计划 成分和配方开发，并已收到FDA的书面意见，以回应我们的 印前调查。该项目的目标是定义疫苗产品，并为全面的CMC和 针对IND应用的药理学/毒理学研究。为了实现这一目标，我们将首先评估 我们的疫苗产品在表达mBRAFp的人类白细胞抗原-1中预防和治疗肿瘤的有效性和安全性 A2转基因小鼠模型，与使用Montanide(临床使用的疫苗)的制剂进行直接比较 佐剂系统)。我们还将探索将疫苗与免疫检查点抑制相结合的可能性 (抗PD1)。然后，我们将开发疫苗成分和最终疫苗产品的分析测试，以及 生成支持IND的数据，以满足FDA的CMC要求。

Abstract Despite the dramatic improvement in outcomes afforded by immune checkpoint inhibitors and targeted therapies, most patients with metastatic BRAF-mutated melanoma ultimately experience progression of their disease. One key reason for resistance to immune checkpoint inhibitors is a paucity of melanoma-specific T cells, but unfortunately, the majority of early melanoma vaccines meant to expand melanoma-specific T cells have failed to demonstrate benefit. Next generation sequencing and in silico peptide-HLA binding prediction have allowed investigators to vaccinate cancer patients against neoantigens – peptides that are not expressed by any normal tissues but are only found in tumors. Although neoantigen vaccines hold great promise, a key limitation is the fact that neoantigens are generally private, thus it is not possible to make an “off-the-shelf” neoantigen vaccine that will be appropriate for a large group of patients. We and others have found that melanoma patients can mount an endogenous T cell response to a mutated BRAF (valine to glutamic acid at position 600). We have further demonstrated that an HLA-A2-binding mutated BRAF peptide (mBRAFp) is highly immunogenic in HLA- A2-transgenic mice. Here we propose that an immunogenic vaccine targeting V600E-mutated BRAF in the context of HLA-A2 has the potential to expand melanoma-specific T cells. As a shared neoantigen, mBRAFp is a relevant tumor target for approximately 20-25% of melanoma patients (40- 50% of melanoma patients harboring BRAF V600E x 50% of patients harboring HLA-A2). This off-the-shelf therapeutic vaccine may be used as a monotherapy for patients with high-risk resected melanoma or with minimal tumor burden. It may also be combined with anti-PD-1 for patients with melanoma that is refractory to immune checkpoint inhibitor therapy and targeted therapy. Our vaccine consists of mBRAFp and resiquimod (RSQ) as adjuvant formulated in CAPRO™ - a new class of proprietary biodegradable liquid polymers, providing local controlled release of both the antigen and adjuvant. Previously we found that (1) mice vaccinated with ovalbumin (OVA) and RSQ loaded in CAPRO developed long-lasting OVA-specific antibody and CD8 T cell responses, and (2) CAPRO-loaded mBRAFp and RSQ elicited antigen-specific T cell response in HLA-A2 transgenic mice. Based on these promising results, we have initiated preclinical product development program involving CMC of the vaccine ingredients and formulation development and have received written comments from the FDA in response to our pre-IND inquiry. The goal of this project is to define the vaccine product and set the stage for full CMC and pharmacology/toxicology studies toward an IND application. To accomplish this goal, we will first evaluate the prophylactic and therapeutic antitumor efficacy and safety of our vaccine product in a mBRAFp-expressing HLA- A2 transgenic mouse model with direct comparison with a formulation using Montanide (a clinically used vaccine adjuvant system). We will also explore the potential of combining vaccine with immune checkpoint inhibition (anti-PD1). We will then develop analytical assays for vaccine ingredients and final vaccine product, and generate IND-enabling data to meet CMC requirements of the FDA.