Overcoming immune checkpoint inhibition with therapeutic plasma exchange and radiotherapy in melanoma

摘要 PD-1导向的免疫检查点抑制剂（ICI）可显著改善转移性黑色素瘤的生存期 与传统化疗相比。不幸的是，不到一半的黑色素瘤患者对ICI有反应， 治疗抗PD 1/PD-L1 ICI耐药性超出黑色素瘤，导致应答率仅为15-35% 对于大多数癌症来说。黑色素瘤分泌导致ICI抗性的因子，包括可溶性PD-L1（sPD-L1） 和PD-L1阳性细胞外囊泡（evPD-L1）。我们最近发现sPD-L1和evPD-L1在 外周血通过与PD-1受体的相互作用直接杀死效应CD 8 + T细胞（图4）。他们 也间接“淬灭”可用的治疗性抗PD-1抗体，导致低ICI应答率（图5）。 因此，迫切需要将这些可溶性形式从循环中去除以拯救黑素瘤患者 从ICI抵抗。 我们先前已经表明，立体定向体部放疗（SBRT）可以改善全身免疫功能， 反应，称为“远位效应”。远位效应是SBRT诱导新生抗原的结果， 炎性细胞因子，上调主要组织相容性复合物和B7家族共刺激因子， 抗原呈递细胞上的分子以募集效应T细胞。不幸的是，远位效应很少被观察到 因此，ICI和放疗联合研究正在进行中。SBRT激活抗- 黑色素瘤免疫通过提供新抗原和危险信号，肿瘤释放这些免疫抑制因子， 细胞外形式的PD-L1杀死活化的效应T细胞（图1）。放射治疗增加肿瘤sPD- L1/evPD-L1释放，我们已经报道了高血浆sPD-L1和/或evPD-L1水平预示着不良的 对治疗和生存的反应。 最近，我们发现治疗性血浆置换（TPE）是一种安全且常用的方法， 其他医学适应症（例如，自身免疫性疾病、重症肌无力、多发性硬化等）的手术， 将sPD-L1和evPD-L1安全地从循环中清除。因此，我们假设， 通过TPE循环sPD-L1和evPD-L1可以克服PD-L1/PD-1介导的免疫调节， 转移性黑色素瘤患者的ICI + SBRT缓解率和生存率如果成功，我们的建议 概念可以在前瞻性随机临床试验中很容易地进行研究，并涉及许多中心， 定期进行TPE。此外，我们的新概念可以在其他PD癌症组织学中进行探索- L1/PD-1耐药，在患者血液中检测到sPD-L1和evPD-L1升高。 图1：PD-L1的细胞外形式（1）evPD-L1和（2）sPD-L1导致对PD-（L）1抑制剂的耐药性 通过竞争性胜过PD-（L）1抑制剂并杀死CD 8+效应T细胞，在癌症治疗中发挥重要作用（也参见图4）。 治疗性抗PD-L1抑制剂的可用性被释放的可溶性PD-L1和evPD-L1“淬灭” 这限制了它的可用性。此外，sPD-L1和evPD-L1可以结合到T细胞表面 PD-1受体和胜过抗PD-1抑制剂。 放疗 肿瘤细胞 1 PD-L1+ EV PD1 免疫细胞 PD-L1抑制剂 ADAM 10/ Adam17 2 PD-L1 PD-1-抑制剂PD 1

ABSTRACT PD-1-directed immune checkpoint inhibitors (ICI) have significantly improved survival in metastatic melanoma compared to traditional chemotherapy. Unfortunately, less than half of patients with melanoma respond to ICI treatment. Anti-PD1/PD-L1 ICI resistance extends beyond melanomas, resulting in a meager 15-35% response rate for most cancers. Melanomas secrete factors that lead to ICI resistance, including soluble PD-L1 (sPD-L1) and PD-L1-positive extracellular vesicles (evPD-L1). We recently discovered that both sPD-L1 and evPD-L1 in the peripheral blood directly kill effector CD8+ T cells through interaction with the PD-1 receptor (Fig 4). They also indirectly “quench” the available therapeutic anti-PD-1 antibody resulting in low ICI response rates (Fig 5). Thus, there is an urgent need to remove these soluble forms from circulation to rescue patients with melanoma from ICI resistance. We have previously shown that stereotactic body radiotherapy (SBRT) can improve systemic immune responses, known as “abscopal effect.” Abscopal effect is the result of SBRT inducing neoantigens, pro- inflammatory cytokines, and up-regulating major histocompatibility complex and B7 family co-stimulatory molecules on antigen presenting cells to recruit effector T cells. Unfortunately, abscopal effect is rarely observed in patient, and therefore, ICI and radiotherapy combination studies are ongoing. While SBRT activates anti- melanoma immunity by providing neoantigens and danger signals, tumors release these immunosuppressive extracellular forms of PD-L1 that kill activated effector T cells (Fig 1). Radiotherapy increases tumor sPD- L1/evPD-L1 release, and we have reported that high plasma sPD-L1 and/or evPD-L1 levels portend poor response to therapy and survival. Recently, we have discovered that therapeutic plasma exchange (TPE), a safe and commonly performed procedure for other medical indications (e.g. autoimmune diseases, myasthenia gravis, multiple sclerosis, etc), removes both sPD-L1 and evPD-L1 safely from the circulation. Therefore, we hypothesize that the removal of circulating sPD-L1 and evPD-L1 by TPE may overcome PD-L1/PD-1-mediated immune regulation to improve ICI + SBRT response rates and survival in patients with metastatic melanoma. If successful, our proposed concept can be readily investigated in a prospective randomized clinical trial and involve many centers that routinely perform TPE. Furthermore, our novel concept can be explored in other cancer histologies with PD- L1/PD-1 resistance where elevated sPD-L1 and evPD-L1 are detected in patients’ blood. Figure 1: Extracellular forms of PD-L1 (1) evPD-L1 and (2) sPD-L1 cause resistance to PD-(L)1 inhibitor therapy in cancer by outcompeting PD-(L)1 inhibitors and killing CD8+ effector T cells (see also Figure 4). The availability of therapeutic anti-PD-L1 inhibitors is “quenched” by soluble PD-L1 and evPD-L1 released from tumor cells which limits its availability. Furthermore, sPD-L1 and evPD-L1 can bind to T cell surface PD-1 receptors and outcompete anti-PD-1 inhibitors. Radiotherapy Tumor Cell 1 PD-L1+ EVs PD1 Immune Cell PD-L1-Inhibitor ADAM10/ ADAM17 2 PD-L1sPD-L1 PD-1-Inhibitor PD1