The majority of PUB patients died of non-bleeding-related causes. Optimization of management should aim at reducing the risk of multiorgan failure and cardiopulmonary death instead of focusing merely on successful hemostasis.
Background: Platelets facilitate hematogenous metastasis in part by promoting cancer cell immunoevasion, although our understanding of platelet function in modulating the adaptive immune system in cancer is limited. A major negative regulator of the adaptive response is the immune checkpoint protein Programmed Death Ligand 1 (PD-L1).Objectives: As platelets secrete factors that may increase PD-L1 expression, we investigated whether they up-regulate cancer cell PD-L1, thus promoting immunoevasion, and whether common anti-platelet drugs inhibit this process.Methods: Platelets were isolated from human volunteers. A549 lung, PD-L1 null A549, and 786-O renal cancer cells were incubated with and without platelets, and cancer cell PD-L1 expression was measured by qPCR and flow cytometry. Additionally, platelet-cancer cell incubations were performed in the presence of common antiplatelet drugs, and with growth factor neutralizing antibodies. Following incubation with platelets, A549 were co-cultured with T-cells and interleukin-2 (IL-2) levels were measured by flow cytometry as a marker of T-cell activation.Results: Platelets increased PD-L1 mRNA and surface protein expression by A549 and 786-0 cells. Combined neutralization of VEGF and PDGF prevented the plateletinduced up-regulation of PD-L1 by A549, as did the anti-platelet drug eptifibatide.A549 incubated with platelets demonstrated a reduced ability to activate human T-cells, an effect reversed by eptifibatide. Conclusions:As platelets promote immunoevasion of the adaptive immune response by increasing cancer cell PD-L1 expression and as anti-platelet drugs prevent this immunoevasive response, the investigation of anti-platelet drugs as adjuvant therapy to immune checkpoint inhibitors may be warranted in the treatment of cancer.
TPS4175 Background: While systemic treatment of PC has improved, rates of surgical resection - considered optimum treatment - remain low. Patients with un-resectable or borderline PC still have poor outcomes, with both toxicity and disease progression during induction chemotherapy limiting the number eligible for surgery. SBRT practice to enhance margin negative resection or to provide local control, if inoperable after neoadjuvant therapy, has shifted to higher dose delivery (Mellon 2015, Colbert 2018), but timing and appropriate patient selection are under constant debate. SBRT delivery over 50Gy exhibits superior cell killing compared to conventionally fractionated RT but carries potential GI toxicity risk (Zhong 2017). GC4711 is a selective superoxide dismutase mimetic that converts superoxide to hydrogen peroxide. As radiation response modifiers, dismutase mimetics have the potential to increase tumor control without compromising radiation safety (Sishc, AACR 2019). GC4711 consistently augmented tumor control by SBRT in PC experimental xenograft mouse models. In a pilot phase 1/2 trial (GC4419-101), subjects with locally advanced PC were randomized to receive SBRT plus either the selective dismutase mimetic GC4419 or placebo. This pilot trial has demonstrated acceptable safety with SBRT (5 × 10-11Gy), as well as apparent improvements in survival, surgical resection, locoregional control, and time to distant metastases. Altogether, these data support the hypothesis that GC4711 may improve tumor outcomes and the benefit-risk ratio of 5-fraction SBRT delivering 50Gy by improving efficacy without increasing GI-toxicity. Methods: GRECO-2 is a phase 2, multicenter, randomized, double-blind, placebo-controlled study to determine the effect on overall survival of adding GC4711 to SBRT following 4 months of chemotherapy in subjects with un-resectable or borderline non-metastatic PC. Approximately 160 subjects will be enrolled at over 20 sites to receive GC4711 100 mg or placebo IV given as IV infusion over 15 min, prior to each of 5 SBRT fractions of 10Gy). Subjects judged operable will be explored within 8 weeks after SBRT. All subjects will complete 2 additional months of adjuvant chemotherapy. Primary end point is overall survival and secondary endpoints address resection rates, local and distant disease progression, and safety, while exploratory studies include ctDNA, tumor exome/transcriptome sequencing, and immune profiling, patient-reported symptoms (PRO-CTCAE), CA19.9 normalization, and radiomics. Colbert L, Rebueno N, Moningi S et al Advances in Radiation Oncology (2018) 3, 693-700 Mellon EA, Hoffe SE, Springett GM, et al Acta Oncologica, 2015;54:7 Zhong J, Patel K, Switchenko J, et al. Cancer. 2017 Sep 15;123(18):3486-3493. Sishc BJ, Saha D, Story MD. AACR PADC 2019 C52. Clinical trial information: NCT04698915.
Introduction: RT-induced SO contributes to initiation of mucosal injury; eg, oral mucositis (OM) and esophagitis. GC4419 specifically mimics SOD’s dismutation of SO to hydrogen peroxide (H2O2), interdicting OM initiation. GC4419 reduced RT-severe OM (SOM) in a hamster cheek pouch model, and protected mucosa and other normal tissues from radiation-induced injury in other animal models. In a published phase 1b/2a open-label trial (Anderson et al, IJROBP, 1 Feb 2018), GC4419 attenuated SOM in patients (Pts) receiving intensity-modulated RT (IMRT) plus concurrent cisplatin (CDDP) for locally advanced head & neck cancer (HNC). Objectives: Determine whether GC4419 reduces duration, incidence, & severity of SOM. Methods: Pts with locally advanced oral cavity or oropharyngeal cancer; definitive or postoperative intensity-modulated (IM)RT (approximately 70 Gy [>50 Gy to > 2 oral sites]) plus CDDP (weekly or q3wk) were randomized (stratification: tumor HPV status, CDDP schedule) to 30 or 90 mg of GC4419, or placebo (PBO), 60-minute IV infusion, M–F, ending <60 minutes before IMRT delivered in 35 fractions over 7 weeks. WHO grade OM was assessed by trained evaluators biw during IMRT & qwk for up to 8 wks after IMRT. Primary endpoint: duration of SOM. Efficacy was tested for each active dose vs PBO (ITT population) by a sequential, conditional approach (2-sided alpha, 0.05). Results: 223 pts (44 sites): 90 mg (n=76), 30 mg (n=73), or PBO (n=74). Baseline patient and tumor characteristics and treatment delivery were balanced. Efficacy: At 90 mg GC4419 vs PBO, duration of SOM was significantly reduced (median, 1.5 vs 19 d; P=.024). SOM incidence (43% vs 65%; P=.009), and grade 4 incidence (16% vs 30%; P=.045) also improved. There were intermediate improvements with 30 mg. Safety was comparable across arms; no significant GC4419-specific toxicity; other known toxicities of IMRT/CDDP were not increased. Conclusions: GC4419 demonstrated a significant, clinically meaningful reduction of SOM duration, and dose-dependent improvements in other SOM parameters, with acceptable safety. A confirmatory phase 3 trial (NCT03689712) is in progress. Clinical trials to reduce RT-related esophagitis are also planned.
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