Abstract CT039: Intratumoral CD40 agonist sotigalimab with pembrolizumab induces broad innate and adaptive immune activation in local and distant tumors in metastatic melanoma

The use of immune-checkpoint inhibitors (CPI) has become an important modality in the treatment of metastatic melanoma (MM). However, most patients (pts) do not experience durable responses and new treatment options are needed to improve clinical outcomes. Our pre-clinical studies have demonstrated that intratumoral CD40 activation synergizes with anti-PD-1 based therapy and induces systemic and distant anti-tumor effects. In this ongoing phase I/II study, we assessed intratumoral sotigalimab (APX005M), a CD40 agonist antibody, in combination with systemic pembrolizumab in CPI treatment naïve, unresectable stage III or IV MM. A total of 40 participants will be enrolled. As of December 15, 2021, 30 pts were enrolled. Pts received sotigalimab every 3 weeks for a total of 4 doses. The dose escalation portion of the trial has been completed, with 14 pts enrolled in 5 dosing cohorts of sotigalimab at 0.1, 0.5, 1, 3 and 10 mg. The primary objectives include safety and tolerability, determination of the recommended phase 2 dose (RP2D), and assessment of the overall response rate (ORR) by RECIST v1.1. Biomarker analyses of blood and tumor samples were performed to measure immune activation using immunophenotyping including imaging mass cytometry, TCR sequencing, and a cross-cohort comparison of gene expression data (sotigalimab plus pembrolizumab versus anti-PD1 monotherapy). The combination therapy has been well-tolerated, and there were no study discontinuations or death due to treatment-related adverse events (TRAEs). Most common TRAEs were injection-site reactions; six pts experienced grade-3 immune-related adverse events. Efficacy analysis of 30 pts with post-baseline disease evaluations demonstrated an ORR of 50% (5 CR and 10 PR) in distant lesions and a disease control rate of 67%. The ORR at the RP2D of 10 mg is 55% (12/22). Responses were observed in PD-L1 negative pts and those with elevated LDH. Comprehensive transcriptome and immune cell profiling of peripheral blood mononuclear cells and tumor biopsies obtained from local lesions at baseline and 24 hours post sotigalimab injection demonstrate that sotigalimab effectively engaged CD40 pathway. In comparison to anti-PD1 monotherapy, the combination therapy significantly increased expression of genes associated with antigen presentation and effector T cells in local lesions accompanied by an increase in T cell activation genes at distant lesions. Additionally, T cell repertoire analysis demonstrated a significant increase in T cell clonality with expansion of new clones shared between local and distant tumors. Importantly, these immunologic changes were correlated with clinical response. Collectively, this combination therapy is well tolerated and has a notable clinical response rate, accompanied by broad innate and adaptive immune activation at both local and distant lesions.

Citation Format: Salah-Eddine Bentebibel, Daniel Johnson, Rodabe Amariae, Daniel McGrail, Srisuda Lecagoonporn, Cara Haymaker, Dzifa Duose, Khalida Wani, Houssein Safa, Isabella Claudia Glitza, Sapna Pradyuman Patel, Michael K. Wong, Hussein Tawbi, Jared Burks, Xiaodong Yang, Patrick Hwu, Cassian Yee, Michael A. Davies, Ravi Murthy, Chantale Bernatchez, Suhendan Ekmekcioglu, Adi Diab, Gregory Lizée. Intratumoral CD40 agonist sotigalimab with pembrolizumab induces broad innate and adaptive immune activation in local and distant tumors in metastatic melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT039.

Immune-related adverse events and symptom burden in patients with melanoma receiving adjuvant immune checkpoint inhibitor

TPS12147

Background: Adjuvant therapy with immune checkpoint inhibitors (ICIs) is approved for melanoma, but immune-related adverse events (irAEs) remain a challenge. Although acute toxicities are well defined, long-term AEs and impact on quality of life (QOL) are undetermined. Available data derived from clinical trials involve highly selected populations and do not reflect real world experience. Additionally, trials measure outcomes only at predetermined endpoints, and symptoms may vary throughout the course of therapy. Moreover, the pathogenesis of irAEs and symptoms remains poorly understood. We hypothesize that AEs and sustained inflammation induced by adjuvant ICIs increase symptom burden and negatively impact function and QOL in a subset of patients (pts), and elevated expression of pro-inflammatory cytokines and T cell signatures during therapy correlate with toxicity and symptom burden. Our preliminary data identified i) interleukin-6/Th-17 pathway as a possible mediator of irAEs, ii) immune reactivity and increases in inflammatory cytokines are associated with symptom burden in cancer survivors, and iii) prioritized 30 genetic markers conferring risk for irAEs in ICI-treated melanoma pts. Methods: This is a prospective longitudinal cohort study to evaluate potential toxicity/symptom burden and immune correlates in melanoma pts receiving adjuvant ICIs (NCT04990726). A total of 240 pts will be enrolled. Eligibility criteria: age ≥18 years (yrs), surgically resected stage II, III, or IV melanoma, initiating adjuvant nivolumab or pembrolizumab, no prior systemic therapy for melanoma, and no prior autoimmune diseases. Patients will be assessed at baseline (before ICI infusion) and every 3 months (mos) up to 2 yrs or until attrition or death. The primary endpoint is the incidence rate of any irAEs at 12 mos. Demographics, personal/family history, comorbidities, tumor history/stage, prior therapies, performance status, concurrent medications, and other factors that play a role in pts perceptions of disease are collected. At each visit, pts undergo a clinical evaluation to assess potential irAEs, new comorbidities, and tumor recurrence. Patient-reported outcomes of fatigue, depression, sleep disturbance, and QOL are collected at each visit to assess changes from baseline up to 2 yrs. In addition to standard methods of data collection at pre-specified times, we leverage mobile technology to capture symptoms and AEs in real time. Longitudinal blood samples will characterize pts immune signatures from baseline up to 2 yrs to evaluate their association with irAEs, symptom burden, and QOL, and to compare the genotype of pts with and without irAEs. To characterize the effect of adjuvant ICI on bone health, eligible pts are evaluated by whole body dual-energy X-ray absorptiometry at baseline and at 12 mos as an exploratory aim. The study is currently active, and 27 pts are enrolled. Clinical trial information: NCT04990726.

Phase 1b study of the novel first-in-class G protein-coupled estrogen receptor (GPER) agonist, LNS8801, in combination with pembrolizumab in patients with immune checkpoint inhibitor (ICI)-relapsed and refractory solid malignancies and dose escalation update

2574

Background: LNS8801 is an oral, highly selective, small molecule agonist of the G protein-coupled estrogen receptor (GPER). LNS8801 normalizes c-Myc levels in cancer cells, inhibits proliferation, suppresses invasion, and enhances immune recognition. In preclinical models, LNS8801 has demonstrated increased activity with ICIs. In the first-in-human dose escalation study, LNS8801 was safe and tolerable alone and in combination with pembrolizumab in patients with metastatic solid tumors (NCT04130516). Methods: Patients who are relapsed and refractory (r/r) to PD-1/L1 ICIs and have measurable disease are enrolling in a Phase 1b cohort and receive LNS8801 (125 mg, QD, PO) and pembrolizumab (200 mg, Q3W, IV) (NCT04130516). The primary objective is safety and tolerability assessed according to NCI CTCAE v5.0. Secondary endpoints include pharmacokinetic, pharmacodynamics (eg., increase in serum prolactin over the initial 10 hours of dosing to assess GPER engagement), objective response rate and clinical benefit rate per RECIST v1.1. Results: Updates from the dose escalation portion of the study include long term benefit in a monotherapy patient with cutaneous melanoma on treatment for 2 years with RECIST stable, metabolically inactive disease by PET; a metastatic uveal melanoma patient on therapy for a year, and growing confidence in LNS8801’s favorable safety profile and predictive systemic biomarkers. As of 2/1/22, 13 ICI r/r patients were treated with LNS8801 and pembrolizumab, including those who entered the study directly after confirmed progression on ICIs. Cancer types include lung (3), colorectal, vaginal, nasopharyngeal, neuroendocrine, uterine, and pancreatic cancer, mesothelioma (2), and cutaneous and uveal melanoma. 46% of patients had AEs possibly related to study drugs (31% grades 1-2 and 31% grade 3), with colitis (15%) and fatigue (23%) appearing in more than 10% of patients. Of the 10 evaluable patients, 7 had stable disease (SD), with 4 patients demonstrating tumor regression. At the data cut-off, duration of treatment ranged from 0.7–7.5 months with 4 patients treated between 4.8 and 7.5 months and 4 patients continuing on treatment. All evaluated patients with SD had a prolactin response indicative of systemic target engagement. Conclusions: The combination of LNS8801 and pembrolizumab is tolerable without unanticipated toxicities and demonstrates encouraging anti-tumor activity in patients that are r/r to ICIs, including patients who enrolled immediately after confirmed progression on pembrolizumab alone. These data, as well as continued follow-up on patients with long-term benefit from dose escalation, support further development of LNS8801 as a cancer therapeutic. Clinical trial information: NCT04130516.

Capturing uveal melanoma (UM) global practice patterns and clinical outcomes in the collaborative ocular melanoma natural history (OMNi) study (NCT04588662)

TPS9610

Background: Geographical differences in the management of primary UM, surveillance for recurrence, and care of metastatic disease have emerged based upon local expertise, treatment availability and insurance coverage. We have initiated accrual to OMNi (NCT04588662), an ambispective database developed to provide contemporary real-world data of UM, capturing its natural history and serving as a virtual biospecimen repository. The overall objectives of OMNi are to characterize regional/international UM management practice patterns and associated clinical outcomes in an effort to inform best practice recommendations. Methods: OMNi utilizes the Pulse Infoframe Healthie platform, a globally compliant platform which enables the structured collection of data mapped to Observational Medical Outcomes Partnership. The data fields created permit longitudinal capture of data including baseline patient and tumor characteristics, treatment of primary lesion and outcomes, surveillance patterns, time to disease recurrence, treatment of recurrent disease with outcomes, and survival. Inclusion criteria include a diagnosis of uveal melanoma and the ability to provide written informed consent for participation in the prospective registry or an institutional waiver by the IRB/ethics committee for retrospective data collection without written informed consent. We have initiated data collection at 3 US and 3 Australian centers, with 184 patients enrolled to date. Based upon feasibility assessment, we anticipate retrospective data entry for ̃2,000 patients and annual recruitment of ̃700 patients once all centers are active. Data collected in this OMNi collaboration, which will include additional US, UK and Australian sites, will facilitate new insights, hypothesis testing, as well as clinical trial development and conduct, and through a governance structure, will be made accessible for research. The OMNi dataset can serve and aid in interpretation of clinical trial outcomes in the real-world, facilitate cutting-edge research, and accelerate the development of diagnostics and therapeutics. Clinical trial information: NCT04588662.

Tocilizumab in combination with ipilimumab and nivolumab in solid tumors

TPS9600

Background: Immune checkpoint inhibitors (ICIs) are approved for multiple malignancies, however, durable remission rates with ICI monotherapy remains low. Combined treatment with anti-CTLA-4 and anti-PD1 has shown higher response rates in several cancers but is associated with up to 60% grade 3/4 immune-related adverse events (irAEs) leading to frequent treatment discontinuation. The need for corticosteroids to control irAEs may further diminish anti-tumor activity. A multi-disciplinary approach using clinical, preclinical, and translational analyses implicated the IL-6/Th17 axis in both ICI-related autoimmunity and resistance. Further, preliminary data showed that targeting interleukin 6 (IL-6) could be an effective approach to reduce irAEs while maintaining and possibly boosting the antitumor immune response. Methods: We are conducting a phase II, open-label, single center study to evaluate the use of combination treatment with tocilizumab (toci; anti-IL6), ipilimumab (ipi; anti-CTLA4) and nivolumab (nivo; anti-PD1) as a front-line therapy for patients (pts) with treatment-naïve advanced cutaneous melanoma (cohort 1), urothelial carcinoma (cohort 2), and EGFR mutant non-small cell lung cancer after tyrosine kinase inhibitors failure (cohort 3) (NCT04940299). Ten pts per disease site will be enrolled, plus an additional 25 melanoma pts in an expansion cohort. Key inclusion criteria are age ≥18 years (yrs) and histologically confirmed locally advanced or metastatic disease, with specific eligibility criteria defined for each cohort. Patients with interstitial lung diseases, autoimmune diseases, infection, or conditions requiring immunosuppressive therapies are not eligible, but stable asymptomatic brain mets are allowed. Ipi/Nivo dosing is as per approved disease indications: in cohort 1 &2, ipi 3 mg/kg + nivo 1 mg/kg is administered intravenously (IV) every 3 weeks (wks) for 4 doses then nivo 480 mg/4 wks up to 2 yrs. In cohort 3, IV ipi 1 mg/kg/6 wks + nivo 3 mg/kg/2 wks is administered up to 2 yrs. In all 3 cohorts, subcutaneous (SQ) toci 162 mg/2wks is administered up to 12 wks. Imaging is every 12 wks up to 2 yrs or until dose-limiting toxicities or progression. The primary outcome is safety/tolerability of the triple therapy. The secondary outcomes are antitumor efficacy and overall survival. Additionally, tumor and blood samples are being collected for longitudinal immune analysis, including gene expression and multiplex histochemistry to identify predictive biomarkers of response, resistance, and toxicity. The trial opened in October 2021 and has enrolled 14 patients to date. Clinical trial information: NCT04940299.

Metabolic complete responses (mCR) in patients with metastatic uveal melanoma (mUM) treated with image-guided injection (IGI) of PV-10

9543

Background: Traditional CT imaging can underestimate the degree of anti-cancer treatment effect due to reliance on morphological changes of visualized tumors. In contrast, PET imaging offers information on metabolic activity using a positron emitting radiolabeled agent (e.g. FDG) but is less sensitive to changes in tumor size. FDG-PET images acquired, co-registered, and superimposed on CT images (PET-CT) allow spatial detection of anti-cancer activity. Moreoever, FDG-PET-CT can provide information regarding anti-tumor immune responses in patients receiving immunotherapy. Rose bengal (PV-10) is a small molecule autolytic immunotherapy in development for metastatic disease. When administered by intralesional injection, PV-10 can produce immunogenic cell death and a T-cell mediated immune response against treatment-refractory and immunologically-cold tumors. Herein, we report the FDG-PET-CT imaging responses of 7 metastatic uveal melanoma (mUM) patients who received percutaneous image-guided injection (IGI) of PV-10 into hepatic tumors. Methods: The Phase 1 study is evaluating safety, tolerability, and efficacy of intralesional PV-10 in hepatic tumors. PV-10 is administered percutaneously via IGI into designated tumors ≤4.9 cm in diameter. Response is assessed at Day 28, then every 3 months, using CT/MRI or PET-CT. Patients with multiple tumors may receive further IGI of PV-10 after Day 28. Results: To date, 25 mUM patients with liver metastases have been treated; 16 patients received standard of care immune checkpoint inhibitor (ICI) during or post PV-10 treatment. Seven subjects had FDG-PET-CT imaging during the study (baseline 1, follow-up 6). Two follow-up FDG-PET-CTs were performed 1 and 3 years after PV-10 injection with intervening ICI, and another was 1.5 years after PV-10, without any follow-on treatment. Four patients experienced mCR in all metastatic sites, including extrahepatic metastasis. Conclusions: FDG-PET-CT shows that PV-10 is capable of inducing mCR in injected (adscopal) and non-injected (abscopal) lesions. This pattern of response is suggestive of immunogenic cell death in mUM patients with liver metastases. Clinical trial information: NCT00986661.

Outcomes of BRAF mutant metastatic melanoma (MM) patients (pts) after cessation of targeted therapy (TT) with BRAF or BRAF/MEK inhibitor(i)

9564

Background: Since their introduction into the clinic a decade ago, BRAF and BRAF/MEKi have dramatically changed the outcomes of pts with BRAF mutant MM. While typically, these agents are administered until progression (PD), other reasons for stopping TT include unacceptable toxicity, complete response to treatment, or pt/physician decision or preference. The outcomes for MM pts that stop TT for reasons other than PD are largely unknown. Here we report the clinical features and outcomes of the largest cohort of MM pts who stopped TT for reasons other than PD to date. Methods: Under an institutionally approved database, we identified MM pts treated at the MD Anderson Cancer Center with BRAF±MEK inhibitors, and their records were reviewed to identify pts that stopped TT for reasons other than PD. Pts demographics, treatment information and clinical outcomes were recorded. Overall survival (OS) time was computed from three start dates (initial diagnosis, initial unresectable stage III melanoma, 1st dose of TT) to last known vital sign. Pts alive at the last follow-up date were censored. Time to recurrence was computed from date of 1st dose of TT to recurrence. Pts who did not experience disease recurrence were censored The Kaplan-Meier method was used to estimate OS and time to recurrence. Results: A total of 58 pts were identified, 32 (55%) were male. Most pts had a BRAF V600E (n = 49) or V600K (n = 6) mutation. At TT initiation median age was 59.5 years (range 29- 95), LDH was within normal range in 46 (85%), median number of prior systemic therapies was 1 (range 0-5), with 50% of pts receiving prior systemic therapy. Most (n = 33; 57%) pts were treated with single agent BRAFi (12 with dabrafenib, 11 vemurafenib). Among pts treated with combination TT (n = 25), most received dabrafenib with trametinib (n = 21; 84%). Median TT treatment duration was 9.5 months (range 0.03-80.5 months). Reasons for TT discontinuation were unacceptable toxicity (n = 29; 50%) and pt or physician decision/preference in responding patients (n = 23; 40%). At time of TT discontinuation, 48% of pts had achieved a complete response (CR), 28% a partial response (PR), and 22% stable disease (SD), 1 patient had unknown disease status. With standard follow-up, after stopping TT, 40 pts (69%) have recurred or experienced PD, with a median time to recurrence of 14.9 months (95% CI:7.8-26.3 months). At PD, 32 (76%) of pts had new metastatic sites. After PD 26 pts (63%) pts received BRAF/MEKi, 11 (44%) achieved a CR and 6 (24%) a PR, and 5 (20%) for a response rate of 88%; while 3 (12%) pt had PD as best response and 1 was unknown. For the full cohort, the median OS from time of 1st dose of TT was 6.4 years. Conclusions: Among MM pts who stopped TT for reasons other than PD, the majority of pts recurred, but most responded to re-introduction of TT. This information can help to inform discussion with pts regarding cessation of, or re-challenge with, TT.

Incidence, timing, and predictors of CNS metastasis in patients (Pts) with clinically localized cutaneous melanoma (CM)

9580

Background: Surveillance for CNS metastasis (mets) is not routinely performed in pts with clinically localized CM. Improved understanding of the incidence, timing and risk factors for the development of CNS metastasis in these pts may inform surveillance strategies. Methods: Under an IRB-approved protocol, demographics, tumor characteristics, and clinical events were collected for pts diagnosed from 1998 to 2019 with AJCC 8th edition stage I or II CM at MD Anderson Cancer Center. Dates of initial diagnosis, regional, distant non-CNS, and CNS mets were recorded. Symptoms and the extent of disease (brain, LMD, both) were recorded for pts with CNS mets. Cumulative incidence of distant mets (CNS and non-CNS) was determined using the competing risks method, including death; pts without CNS mets and alive at last follow-up were censored. Differences in cumulative incidence between groups were assessed using Gray’s test. Associations between measures of interest and cumulative incidence were determined using proportional subdistribution hazards regression models. All statistical tests used a significance level of 5%. Results: 5,179 Stage I-II CM pts were identified. At a median follow up of 82 (0.0-268.8) months, 703 (13.6%) pts were diagnosed with distant mets, including 355 (6.9%) with CNS mets. Cumulative incidence of CNS mets was 0%, 2%, and 5% at 1, 2, and 5 years, respectively. Among pts with distant mets, the first site of distant mets was CNS only for 29 (4%), non-CNS only for 557 (79%), and both for 116 (17%) pts. At initial diagnosis of CNS mets, 195 (55%) pts were asymptomatic, and 46 (13%) had no active extracranial disease. Median time to any distant met was longer for pts who were diagnosed with CNS mets [40.0 (1.9-238.0) months] vs pts diagnosed with non-CNS mets only [31.4 (1.1-185.7) months, p < 0.001]. On multivariable analysis, risk of CNS mets was significantly associated with primary tumor location of scalp [Hazard Ratio (HR) 3.4, 95% Confidence interval (CI) 1.9-5.9], head/neck (HR 3.3, 95% CI 2.0-5.3), or trunk (HR 2.3, 95% CI 1.5-3.5) (vs upper extremity); acral lentiginous melanoma subtype (HR 2.0, 95% CI 1.2-3.6) (vs superficial spreading); increased T category (T2 HR 1.5, 95% CI 1.1-2.2; T3 HR 1.9, 95% CI 1.2-3.0; T4 HR 2.1, 95% CI 1.1-3.8; vs T1), Clark level (CL) (CL4 HR 2.1, 95% CI 1.2-3.7 vs CL2), and mitotic rate (MR) (MR 5-9/mm2 HR 2.1, 95% CI 1.5-3.0; MR > 9/mm2 HR 2.0, 95% CI 1.3-3.0; vs MR 0-4/mm2). While high ( > 9/mm2) MR was associated with increased risk of CNS and non-CNS mets, intermediate (5-9/mm2) was associated with CNS mets only. Conclusions: Primary tumor location, tumor thickness, and MR were strongly associated with risk of CNS mets. MR rate was more strongly associated with risk of CNS than non-CNS mets. Validation in independent cohorts may provide evidence to support CNS surveillance strategies in select pts with stage I-II CM who are deemed high risk for CNS mets.

Early safety and efficacy from a phase I open-label clinical trial of CD137(4-1BB) agonistic antibody LVGN6051 as monotherapy and in combination with pembrolizumab

2521

Background: LVGN6051, a monoclonal antibody against CD137 (also known as 4-1BB or TNFRSF9) with an engineered Fc capable of selectively binding to the Fcγ receptor IIB, acts as a conditional CD137 agonist, resulting in immune activation optimally in tumor microenvironment ( Qi, Nat. Commun. 2019 ). In preclinical models, LVGN6051 demonstrated robust anti-tumor efficacy and safety as a single agent and in combination with anti-PD-1 antibodies. Therefore, we have initiated this first-in-human study of LVGN6051 alone or in combination with pembrolizumab for the treatment of advanced or metastatic malignancy. Methods: This study includes accelerated dose escalation monotherapy up to 2 mg/kg of LVGN6051, and traditional 3 + 3 design for higher doses of LVGN6051 alone or in combination with pembrolizumab. Then, this study will enroll patients with specific types of malignancies following Simon’s two-stage design. Both agents are administered once every 3 weeks. Primary objectives of this study were to define the safety profile and to establish the recommended phase 2 dose (RP2D) of LVGN6051 alone or in combination with pembrolizumab. Pharmacokinetics, immunogenicity, pharmacodynamics and clinical efficacy will be also evaluated. Results: At the cut-off date on January 18, 2021, 16 subjects have been enrolled into the monotherapy cohorts (n=12, no DLT observed up to 7 mg/kg), and the combination cohort (n=4, ongoing at LVGN6051 2 mg/kg and pembrolizumab 200 mg, one DLT observed). No treatment-related adverse event (TRAE) was observed in monotherapy. Treatment-emergent adverse events (TEAE) in combination included increased ALT/AST, thrombocytopenia, and fatigue. In the combination cohort, one patient with predominant hepatic metastases and history of intermittent grade 2 hepatic impairment experienced grade 3 increased ALT/AST (DLT) on cycle 1 day 15 that were resolved to her baseline without corticosteroids on cycle 1 day 18. TRAE included increased ALT/AST, thrombocytopenia, neutropenia, nausea and fatigue. Seven of 10 evaluable patients in the monotherapy cohorts demonstrated stable disease with the longest treatment being 8+ months. Tumor reductions by >10% were observed in melanoma and neuroendocrine tumor on monotherapy. One patient with metastatic head and neck squamous cell carcinoma who had progressed on an anti-PD-L1 based therapy showed an immune partial response (iPR) for 6+ months to the combination therapy. Conclusions: Preliminary evidence showed that LVGN6051 was well tolerated and tumor shrinkages were observed. While we continue assessing its safety profile, antitumor activity was observed in the LVGN6051 and pembrolizumab cohort. The favorable safety profile and preliminary antitumor activity warrant further evaluation in patients with advanced malignancies. Clinical trial information: NCT04130542.

Final analysis of overall survival (OS) and relapse-free-survival (RFS) in the intergroup S1404 phase III randomized trial comparing either high-dose interferon (HDI) or ipilimumab to pembrolizumab in patients with high-risk resected melanoma

9501

Background: We assessed whether or not adjuvant pembrolizumab given over 1 year would improve OS and RFS in comparison to high dose ipilimumab (ipi10) or HDI - the two FDA-approved adjuvant treatments for high risk resected melanoma at the time of study design. Methods: Patients age 18 or greater with resected stages IIIA(N2), B, C and IV were eligible. Patients with CNS metastasis were excluded. At entry, patients must have had complete staging and adequate surgery to render them free of melanoma including completion lymph node dissection for those with sentinel node positive disease. Prior therapy with PD-1 blockade, ipilimumab or interferon was not allowed. Two treatment arms were assigned based on stratification by stage, PD-L1 status (positive vs. negative vs. unknown), and intended control arm (HDI vs. Ipi10). Patients enrolled between 10/2015 and 8/2017 were randomized 1:1 to either the control arm [(1) interferon alfa-2b 20 MU/m2 IV days 1-5, weeks 1-4, followed by 10 MU/m2/d SC days 1, 3, and 5, weeks 5-52 (n=190), or (2) ipilimumab 10 mg/kg IV q3w for 4 doses, then q12w for up to 3 years (n=465)], or the experimental arm [pembrolizumab 200 mg IV q3w for 52 weeks (n=648)]. The study had three primary comparisons: 1) RFS among all patients, 2) OS among all patients, 3) OS among patients with PD-L1+ baseline biopsies. Results: 1,426 patients were screened and 1,345 patients were randomized with 11%, 49%, 34%, and 6% AJCC7 stage IIIA(N2), IIIB, IIIC and IV, respectively. This final analysis was performed per-protocol 3.5 years from the date the last patient was randomized, with 512 RFS and 199 OS events. The pembrolizumab group had a statistically significant improvement in RFS compared to the control group (pooled HDI and ipi10) with HR 0.740 (99.618% CI, 0.571 to 0.958). There was no statistically signifcant improvement in OS in the 1,303 eligible randomized overall patient population with HR 0.837 (96.3% CI, 0.622 to 1.297), or among the 1,070 (82%) patients with PD-L1 positive baseline biopsies with HR 0.883 (97.8% CI, 0.604 to 1.291). Gr 3/4/5 event rates were as follows: HDI 69/9/0%, ipi10 43/5/0.5% and pembrolizumab 17/2/0.3%. Conclusions: Pembrolizumab improves RFS but not OS compared to HDI or ipi10 in the adjuvant treatment of patients with high-risk resected melanoma. Pembrolizumab is a better tolerated adjuvant treatment regimen than HDI or Ipi10. Support: NIH/NCI NCTN grants CA180888, CA180819, CA180820, CA180863; and in part by Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA. Editorial Acknowledgement: With special thanks to Elad Sharon, MD, MPH, and Larissa Korde, MD, MPH. National Cancer Institute, Investigational Drug Branch, for their contributions to this trial, as well as Nageatte Ibrahim, MD, and Sama Ahsan, MD Merck. Clinical trial information: NCT02506153.

Patients with advanced solid cancers treated with ERK inhibitors exhibit pseudo-progession in lymphatic nodes

3138

Background: ERK1/2 signaling is often overactivated in cancer, especially in patients with molecular alterations activating the MAPK pathway. MAPK pathway inhibition can result in the increase of CD8+ and CD4+ T-cells and decreased expression of immunosuppressive cytokines. Methods: This is a retrospective study of 52 patients with advanced solid cancers and oncogenic alterations in the MAPK pathway, who were treated in phase I/II clinical trials with five different single agent ERK1/2 inhibitors at MD Anderson Cancer Center. We reviewed serial PET and/or CT imaging obtained before therapy, on therapy, and after therapy completion. We evaluated dynamic changes in the lymphatic nodes (LN) in the context of overall response per RECIST 1.1 and other outcomes. Results: Of the 52 patients, 19 (37%) patients were evaluated with serial PET/CT and 33 (63%) with serial CT imaging only. Of the 19 patients evaluated with PET/CT, 12 (63%) demonstrated increased FDG uptake in LN compared to pre-treatment imaging (LN enlargement, n = 9; no LN enlargement, n = 3) discrepant from the known target and non-target lesions. These 12 patients were on therapy with ERK inhibitors (11 at doses > recommended phase 2 dose [RP2D]) for a median of 3.6 months (range, 1.8-12 months) with a best response per RECIST 1.1. as follows: partial response, n = 1; stable disease (SD), n = 10; progressive disease (PD), n = 1. Of interest, in 6 of those 12 patients, FDG uptake in LN decreased or resolved after treatment discontinuation. Further, one patient had a biopsy of an emerged LN, which showed lymphocytic infiltrate without tumor cells. Of the 33 patients evaluated with CT only, 5 (15%) demonstrated increased size of LN discrepant from the known target and non-target lesions compared to pre-treatment imaging. These 5 patients were on therapy with ERK inhibitors (all at doses < RP2D) for a median of 1.4 months (range, 1.1-3.5 months) with a best response per RECIST 1.1. as follows: SD, n = 2; PD, n = 3. Of interest, in 2 of those 5 patients, size of LN decreased or resolved after treatment discontinuation. In addition, one patient had a biopsy of an emerged LN, which showed lymphoid aggerates without tumor cells. Conclusions: Our data suggest that treatment with ERK inhibitors can result in activation of the lymphatic nodes, which can manifest as pseudo-progression. This can lead to an inconclusive assessment of their therapeutic benefit and further suggests exploration of the potential synergistic effects with immune therapy.

Neoadjuvant and adjuvant nivolumab (nivo) with anti-LAG3 antibody relatlimab (rela) for patients (pts) with resectable clinical stage III melanoma

9502

Background: Neoadjuvant therapy (NT) for pts with clinical stage III melanoma remains an active area of research interest. Recent NT trial data demonstrates that achieving a pathologic complete response (pCR) correlates with improved relapse-free (RFS) and overall survival (OS). Checkpoint inhibitor (CPI) NT with either high or low dose ipilimumab and nivolumab regimens produces a high pCR rate of 30-45% but with grade 3-4 toxicity rate of 20-90%. In metastatic melanoma (MM), the combination of nivo with rela (anti Lymphocyte Activation Gene-3 antibody) has demonstrated a favorable toxicity profile and responses in both CPI-naïve and refractory MM. We hypothesized that NT with nivo + rela will safely achieve high pCR rates and provide insights into mechanisms of response and resistance to this regimen. Methods: We conducted a multi-institutional, investigator-initiated single arm study (NCT02519322) enrolling pts with clinical stage III or oligometastatic stage IV melanoma with RECIST 1.1 measurable, surgically-resectable disease. Pts were enrolled at 2 sites and received nivo 480mg IV with rela 160mg IV on wks 1 and 5. Radiographic response (RECIST 1.1) was assessed after completion of NT; surgery was conducted at wk 9 and specimens were assessed for pathologic response per established criteria. Pts received up to 10 additional doses of nivo and rela after surgery, with scans every 3 mo to assess for recurrence. The primary study objective was determination of pCR rate. Secondary objectives included safety, radiographic response by RECIST 1.1, event-free survival (EFS), RFS, and OS analyses. Blood and tissue were collected at baseline, at day 15, day 28, and at surgery for correlative analyses. Results: A total of 30 pts (19 males, median age 60) were enrolled with clinical stage IIIB/IIIC/IIID/IV (M1a) in 18/8/2/2 pts, respectively. 29 pts underwent surgery; 1 pt developed distant metastatic disease while on NT. pCR rate was 59% and near pCR ( < 10% viable tumor) was 7% for a major pathologic response (MPR, pCR + near pCR) of 66%. 7% of pts achieved a pPR (10-50% viable tumor) and 27% pNR (≥50% viable tumor). RECIST ORR was 57%. With a median follow up of 16.2 mos, the 1 -year EFS was 90%, RFS was 93%, and OS was 95%. 1-year RFS for MPR was 100% compared to 80% for non-MPR pts (p = 0.016). There were no treatment related gr 3/4 AEs that arose during NT; 26% of pts had a gr 3/4 AE that began during adjuvant treatment. Conclusions: Neoadjuvant and adjuvant treatment with nivo and rela achieved high pCR and MPR rates with a favorable toxicity profile in the neoadjuvant and adjuvant settings. Pts with MPR had improved outcomes compared to non-MPR pts. Translational studies to discern mechanisms of response and resistance to this combination are underway. Clinical trial information: NCT02519322.

Phase II Study of TRIplet combination Nivolumab (N) with Dabrafenib (D) and Trametinib (T) (TRIDeNT) in patients (pts) with PD-1 naïve or refractory BRAF-mutated metastatic melanoma (MM) with or without active brain metastases

9520

Background: Targeted therapies (TT) & immunotherapies (IMT) have improved survival for pts with BRAF V600 mutated stage IV MM, however many pts still progress and ultimately die from their disease. Preclinical data support the rationale for combining TT and IMT, but trials evaluating triplet combinations in IMT-naïve pts have reported mixed results. Notably, pts with untreated brain metastases (BM) were excluded from prior triplet trials and have a median PFS of 5.6 months when treated with TT. Further, there remains an unmet need for effective therapies for pts after IMT failure, as retrospective studies have reported short median PFS (5 mos) for TT in this setting. We hypothesized that N in combination with DT is safe and will demonstrate clinical activity in BRAF-mutated pts naïve or refractory to PD1 therapy and in pts with BM. Methods: We conducted a single arm phase II study (NCT02910700) of NDT in pts with BRAF-mutated, unresectable stg III or stg IV MM. Prior IMT was allowed, but prior BRAF/MEKi was not. Pts with untreated BM and asymptomatic or mildly symptomatic/requiring steroids were also allowed. Pts received 3mg/kg IV Q2wks of N (later amended to 480 mg IV Q4wks), 150mg PO BID of D and 2mg PO QD of T, all starting on Day 1. The primary objective was to determine safety and efficacy (ORR by RECIST 1.1). Monitoring for safety and futility using Bayesian stopping rules was performed. Longitudinal tissue and blood samples were collected to perform correlative analyses. Results: Following a 6 pt safety run-in with no observed DLTs, 27 pts were treated w NDT. 17 pts were PD1 refractory, 10 were PD-1 naïve. 10 of these 27 pts had a history or presence of BM, including active BM. Median follow up was 18.4 months (range 3.2-45.9). ORR in 26 evaluable pts was 92% (3 CR, 21 PR). Among the PD1 refractory pts evaluable for response (n = 16), ORR was 88% (2 CRs, 12 PR). All 10 evaluable PD-1 naïve pts achieved a response. 4 of 7 evaluable pts w BM achieved an intracranial response (57%), including 2 CRs. The median PFS for all pts was 8.5mos (8.5mos in PD1 naïve pts, 8.2mos in PD1 refractory pts). Median PFS for pts without BM was 8.5mos, 8.0 mos for those with BM. Median OS for all pts was not reached, and no statistically significantly difference in OS by PD1 exposure or presence of BM. 78% of pts experienced treatment related grade 3/4 AEs and 6 pts (22%) discontinued all 3 drugs due to toxicities. Conclusions: NDT at full doses of all 3 agents has a toxicity profile consistent with previously reported triplet combinations and shows promising clinical activity in pts with IMT refractory disease and with BM. There were no significant differences in outcomes between pts with and without BM. Translational studies to delineate predictors and mechanisms of response and resistance are ongoing. Clinical trial information: NCT02910700.

S1801: A randomized trial of adjuvant versus neoadjuvant pembrolizumab for melanoma

TPS9585

Background: Although long term outcomes for most patients with early-stage melanoma is excellent following surgery, patients who have high-risk features such as lymph node involvement have poorer outcomes. Adjuvant therapy (AT) is currently considered for patients with stage III melanoma and selected patients with resected stage IV melanoma. Currently, AT for melanoma is anti-PD-1 or targeted therapy in the presence of a BRAF mutation. At this time, we are not able to predict which patients will derive benefit from AT and experience cure. While curative intent is the goal of treatment for primary melanoma, patients with bulky nodal involvement are at high risk of local or distant recurrence despite upfront surgery. Neoadjuvant treatment (NAT) offers the benefit of an early on-treatment pathological sample that can be profiled for biomarkers and correlated with response and survival. Treating with anti-PD1 while tumor remains visible in the body may generate a stronger immune response against in vivo tumor antigens compared to the traditional adjuvant setting where antigen is presented by microscopic residual tumor burden. Pilot studies of NAT with anti-PD-1 therapy have been initiated in melanoma. Multidisciplinary coordination in these cases is paramount. In these studies, an improvement in relapse-free survival and overall survival has been observed; additionally, pathologic response rates to NAT have been estimated in small studies. Methods: S1801 is a randomized phase II study of AT versus NAT with pembrolizumab (PEM, NCT03698019). Patients with measurable, clinically detectable and resectable cutaneous, acral, and mucosal melanomas without brain metastasis are eligible. Patients with Stage IIIB to oligometastatic, resectable Stage IV are randomized 1:1 to AT or NAT. Patients getting AT undergo surgery first followed by 18 doses of PEM 200 mg IV every 3 weeks. Patients getting NAT receive 3 doses of pre-operative PEM followed by surgery and then 15 doses of adjuvant PEM. Radiation may be given on either arm after surgery, at the investigator’s discretion. Primary endpoint is event-free survival measured from the date of randomization to the date of first documented progression that renders the patient unable to receive planned protocol surgery, failure to begin adjuvant therapy within 84 days of surgery, relapse after surgery, or death due to any cause. Secondary endpoints include RECIST and iRECIST response rates, as well as a number of surgical outcomes. Safety monitoring is conducted with disease progression and toxicity thresholds. The key Translational Medicine objective of this trial is to determine the pathologic response rate to NAT after 3 doses of PEM. Surgical pathology grossing instructions to ensure readout for pathologic response are provided in the form of training slides. Enrollment is at 40% of a planned 500 patients. Clinical trial information: NCT03698019.

Targeting innate immunity with BXCL701 in combination with pembrolizumab in patients with advanced solid cancers: Phase 2 basket study

2558

Background: BXCL701 is an oral competitive inhibitor of dipeptidyl peptidases (DPPs), primarily DPP8/9, which triggers the inflammasome to alert and prime immune cells, leading to induction of IL-18 and IL-1ß. BXCL701 therefore, can induce an innate immune reaction and tumor inflammation, bridging between innate and adaptive immunity, potentially leading to synergistic anticancer activity when combined with PD-1 antibody pembrolizumab. Methods: This is a phase 2, open-label, single-center study (NCT04171219) of oral BXCL701 0.3 mg BID on days 1-14 and intravenous pembrolizumab 200 mg on day 1 of a 21-day cycle with a safety lead-in to evaluate RECIST/iRECIST response rate in patients with advanced solid cancers. After confirming safety and dose limiting toxicities (DLT) in the first 6 patients, additional patients are being enrolled to an immune checkpoint inhibitors (iCPI) naïve cohort and iCPI pretreated cohort. Each cohort is planned to enroll 9 patients in the first stage, and if a partial (PR) or complete response (CR) is observed the cohort is expanded to a total of 17 patients in the second stage. The treatment is considered promising if at least 3 PRs or CRs are observed in a cohort of 17 patients. Results: As of February 11, 2021, 16 patients were treated; 5 patients (prostate cancer, endometrial cancer, liposarcoma, basal cell carcinoma, squamous cell carcinoma of unknown primary) were enrolled in the iCPI naïve cohort and 11 patients (leiomyosarcoma [2], squamous cell carcinoma of unknown primary, triple negative breast cancer, uveal melanoma, melanoma, uterine myxoid sarcoma, pleomorphic sarcoma, colorectal cancer, anaplastic astrocytoma, prostate cancer) were enrolled to iCPI pretreated cohort. Among all 16 patients, there was 1 episode of grade 4 hypotension (recovered) and 1 episode of grade 5 hypotension attributed to BXCL701, which resulted in implementation of risk-mitigation strategies such as gradual dose escalation and blood pressure monitoring. In the CPI naïve cohort, of 4 patients with available imaging, 1 had a PR (microsatellite stable endometrial cancer [-62%]) and 1 durable stable disease (SD -10%, basal cell carcinoma on therapy for 6+ months). In the CPI pretreated cohort, of 9 patients with available imaging, 1 had a PR (-31%, uveal melanoma) and 3 durable SD (-22%, pleomorphic sarcoma on therapy for 8+ months; +4%, squamous cell carcinoma of unknown primary on therapy for 6 months; +5%, uterine myxoid sarcoma on therapy for 6 months). Conclusions: BXCL701 in combination with pembrolizumab demonstrated encouraging signals of activity in selected difficult-to-treat cancers. Prespecified efficacy endpoints were met in the first stage and both cohorts will proceed to second-stage of the study Clinical trial information: NCT04171219.

Management of early melanoma recurrence despite adjuvant anti-PD-1 antibody therapy☆

BACKGROUND

Anti-programmed cell death protein 1 (PD-1) antibodies (PD1) prolong recurrence-free survival in high-risk resected melanoma; however, approximately 25%-30% of patients recur within 1 year. This study describes the pattern of recurrence, management and outcomes of patients who recur with adjuvant PD1 therapy.

PATIENTS AND METHODS

Consecutive patients from 16 centres who recurred having received adjuvant PD1 therapy for resected stage III/IV melanoma were studied. Recurrence characteristics, management and outcomes were examined; patients with mucosal melanoma were analysed separately.

RESULTS

Melanoma recurrence occurred in 147 (17%) of ∼850 patients treated with adjuvant PD1. In those with cutaneous melanoma (n = 136), median time to recurrence was 4.6 months (range 0.3-35.7); 104 (76%) recurred during (ON) adjuvant PD1 after a median 3.2 months and 32 (24%) following (OFF) treatment cessation after a median 12.5 months, including in 21 (15%) who ceased early for toxicity. Fifty-nine (43%) recurred with locoregional disease only and 77 (57%) with distant disease. Of those who recurred locally, 22/59 (37%) subsequently recurred distantly. Eighty-nine (65%) patients received systemic therapy after recurrence. Of those who recurred ON adjuvant PD1, none (0/6) responded to PD1 alone; 8/33 assessable patients (24%) responded to ipilimumab (alone or in combination with PD1) and 18/23 (78%) responded to BRAF/MEK inhibitors. Of those who recurred OFF adjuvant PD1, two out of five (40%) responded to PD1 monotherapy, two out of five (40%) responded to ipilimumab-based therapy and 9/10 (90%) responded to BRAF/MEK inhibitors.

CONCLUSIONS

Most patients who recur early despite adjuvant PD1 develop distant metastases. In those who recur ON adjuvant PD1, there is minimal activity of further PD1 monotherapy, but ipilimumab (alone or in combination with PD1) and BRAF/MEK inhibitors have clinical utility. Retreatment with PD1 may have activity in select patients who recur OFF PD1.

Phase II single-arm multi-center study of adjuvant ipilimumab in combination with nivolumab in subjects with high-risk ocular melanoma

TPS10089

Background: Treatment of primary ocular melanoma is often very effective, with local recurrence rates of < 5%. However, distant recurrence is as high as 50% depending on features of the primary tumor. These data emphasize the need for effective adjuvant therapy for patients with locally treated ocular melanoma. Several adjuvant treatments have been developed for patients with high-risk cutaneous melanoma, including ipilimumab and nivolumab monotherapies and an ongoing trial is exploring the nivolumab/ipilimumab combination (CA209-915), but patients with high-risk ocular melanomas have been excluded from these trials. As yet there is no approved adjuvant treatment for high-risk ocular melanoma patients. Methods: We are conducting a Phase II single-arm multi-center study of adjuvant ipilimumab in combination with nivolumab in subjects with high-risk ocular melanoma. This study aims to generate efficacy and safety data for adjuvant this regimen in patients with locally treated high-risk ocular melanoma with 3-year risk of relapse > 50%. The primary endpoint is 3-year relapse-free survival rate. Secondary endpoints are median relapse-free survival, median overall survival, 3-year overall survival rate and safety. All patients will receive nivolumab 240mg IV every 2 weeks plus ipilimumab 1mg/kg IV every 6 weeks. Subjects may receive up to 25 doses of nivolumab and 8 doses of ipilimumab. The accrual goal is 50 patients across all participating institutions. Subjects treated in this study will be matched with controls selected from a contemporaneously collected OM registry, “contemporaneous control” in order to better assess efficacy. Control subjects will be from institutions not participating in this trial, will otherwise meet the trial eligibility criteria and will be further matched with trial participants for various demographic and risk factors to the extent possible. The study is enrolling in 6 comprehensive cancer centers in the US. Clinical trial information: NCT3528408.

Radiomic signatures to predict response to targeted therapy and immune checkpoint blockade in melanoma patients (pts) on neoadjuvant therapy

10067

Background: Metastatic melanoma pt outcomes have been revolutionized by targeted therapy (TT) and immune checkpoint blockade (ICB), which are now being evaluated in the neoadjuvant (neoadj) setting. While tumor-based biomarkers may help predict response, predictors of response obtained by less invasive strategies could greatly benefit pt care and allow real-time treatment response monitoring. Radiomic signatures derived from computerized tomography (CT) images have recently been shown to predict response to ICB in stage IV pts. However, the association of radiomic features with pathological response following neoadj therapy has not been assessed. We sought to determine if radiomic assessment predicts pCR in pts receiving neoadj TT and ICB. Methods: We collected data for a cohort of melanoma pts with locoregional metastases who were treated with neoadj TT (n = 33) or ICB (n = 30). Pts received systemic therapy for 8-10 weeks prior to planned surgical resection. Responses were evaluated radiographically (RECIST 1.1) and via pathological assessment (evaluating for pathologic complete response; (pCR) versus < pCR). Thirty two pts (19 ICB; 13 TT) were included in the radiomics analysis based on the availability of appropriate CT imaging. A total of 310 unique radiomic features (10 histogram-based and 300 second-order texture features) were calculated from each extracted volume of interest (VOI). Feature extraction was performed on baseline and initial on-treatment pre-operative CT scans. Features associated with pCR were assessed using a feature selection approach based on Least Absolute Shrinkage and Selection Operator (LASSO). Selected features were used to build a classification model for prediction of pCR to ICB or TT. Leave-One-Out Cross-Validation was performed to evaluate the robustness of the estimates. Results: Out of 310 radiomic features, three features measured at baseline were able to predict a pCR to neoadj ICB or TT with sensitivity, specificity and accuracy of 100%, though these signatures were non-overlapping. In the on-treatment pre-operative scans, 3 distinct features (also non-overlapping and distinct from the predictive pre-treatment signatures) also predicted pCR to ICB and TT with 100% sensitivity, specificity and accuracy. Conclusions: Radiomic signatures in baseline and on-treatment CT scans accurately predict pCR in melanoma pts with locoregional metastases treated with neoadj TT or ICB. These provocative findings warrant further investigation in larger, independent cohorts.

Safety results from phase I/II study of the PI3Kβ inhibitor GSK2636771 (G) in combination with pembrolizumab (P) in patients (pts) with PD-1 refractory metastatic melanoma (MM) and PTEN loss

e22000

Background: Checkpoint inhibitors (CPI) have improved survival and long-term disease control in 35-40% of pts with MM. Many pts derive no clinical benefit or progress after an initial response. Our group and others have shown that loss of the tumor suppressor protein PTEN occurs in multiple cancers, up to 30% of MM pts, activates the PI3K pathway, and correlates with decreased MM response rates to CPI and decreased T cell infiltrates. In PTEN-null MM preclinical models, inhibition of the PI3Kβ-subunit with GSK2636771 (G) was superior to pan-PI3K inhibitors, increased intratumoral T cell infiltration and the activity of CPI. To test our hypothesis that PI3Kβi reverses resistance to CPI, we are conducting a Phase I/II study (NCT03131908) combining G with P in PD-1 refractory pts with PTEN loss. Methods: The primary objective of Ph I portion is to determine the Maximum-Tolerated Dose (MTD) and Recommended Phase II Dose (RP2D) of G with P in PD-1 refractory pts (including melanoma, endometrial, TNBC, and prostate cancers) with PTEN loss. Pts receive P at 200mg IV q 3 wks. G starting dose level (DL1) was 300 mg PO qd for 21 days and escalated to 400 mg PO qd (DL2) using a 3+3 design. A dose level -1 (DL-1) (200 mg PO qd) was also included in the event of unacceptable toxicities at higher doses. Ph II will accrue 35 pts at the RP2D. This study is continuously monitored for toxicity and futility. The primary objectives of Ph II are safety, tolerability, and efficacy of the combination as defined by Objective Response Rate (ORR) by RECIST 1.1. Secondary Objectives include the PKs of G and PD effects in tumor tissue as measured by pathway inhibition and T cell trafficking into tumors. Results: 13 pts have been treated, 6 at the 300mg (DL1), 5 at 400mg (DL2), and 2 at 200 mg (DL-1). One DLT (grade 3 hypocalcemia) was observed at the 300mg dose. Two DLTs were observed in the 400mg cohort, one of which was AKI requiring dialysis and the other was a Gr 3 rash. Based on this experience and additional safety data from GSK regarding renal toxicity, DL-1 was declared RP2D at 200mg. 2 pts at the RP2D have passed the DLT evaluation period without toxicities. Conclusions: The combination of G and P is being explored at the RP2D of 200 mg. Renal toxicity precluded higher doses. No objective responses have been observed although 2 pts have experienced prolonged clinical benefit including a MM pt with 27% decrease in tumor burden. Through longitudinal biopsies, we aim to better understand the role PTEN loss plays when targeted in combination with CPI. Clinical trial information: NCT03131908.

Percutaneous hepatic injection of rose bengal disodium (PV-10) in metastatic uveal melanoma

3143

Background: PV-10 is a small molecule autolytic immunotherapy in clinical development for treatment of solid tumors. When administered by intralesional (IL) injection, PV-10 can produce immunogenic cell death that may induce a T cell-mediated immune response against treatment refractory and immunologically cold tumors. Given this mechanism of action and clinical data that metastatic uveal melanoma (MUM) generates low response rates to immune checkpoint blockade (CB), we investigated treatment of MUM with percutaneously-delivered PV-10. Methods: This open-label Phase 1 basket study (NCT00986661) is evaluating the safety, tolerability, and preliminary efficacy of intralesional PV-10 in patients (pts) with solid tumors of the liver. PV-10 is injected into one or more designated hepatic tumor(s) with a maximum sum of diameters ≤4.9 cm. Response assessments using 2D EASL criteria are performed at Day 28, then every 3 months. Pts with additional injectable tumors are eligible to receive further PV-10 after Day 28. Pts can receive standard of care CB immunotherapy during treatment with PV-10. Results: As of February 1, 2020, the initial cohort of 15 pts with MUM to the liver was fully enrolled. Pts had received at least 1 IL injection of PV-10, with an average of 2 hepatic lesions injected per pt (range 1-4). Of these, 4 pts were refractory to prior CB. Three pts received PV-10 alone, 3 received PV-10 + anti-PD-1 and 9 received PV-10 + anti-PD-1 + anti-CTLA-4. Adverse events (AEs) were consistent with established patterns for PV-10 and CB: AEs attributed to PV-10 were transient and included 3 cases of Grade 3/4 transaminitis that resolved within 72 hrs, injection site pain, photosensitivity, and pink discoloration of skin, urine or feces; AEs attributed to CB included nausea, decreased WBC, and fatigue. Response assessments on 24 injected tumors were: 2 complete response (8%), 7 partial response (29%) and 11 stable disease (46%), per 2D EASL. Among the 4 CB-refractory pts, median overall survival (OS) was 9.2 months (range 5.3 - 11.4 months, with 2 pts alive at 5.3 months each), while among the 11 CB-naïve pts OS was undefined (range 0.5 - 21.9+ months, with 1 death at 7.9 months). Pts receiving PV-10 alone (1 CB-refractory, 2 naïve) achieved a median OS of 7.9 months with one CB-naïve pt alive with partial overall response at 21.9 months. Conclusions: Response indicative of regression or stabilization in a majority (83%) of injected lesions is encouraging in a disease of major unmet need. Enrollment and follow-up for safety, duration of response and survival are ongoing. Clinical trial information: NCT00986661 .

Intratumor immunotherapy utilizing real time radiological image guidance: Early experience from a tertiary cancer center

e15223

Background: Intratumoral (IT) delivery of immunotherapeutic agents is a compelling approach to overcoming the systemic barriers of toxicity and lack of efficacy associated with many novel agents. In this context, the application of IT delivery is growing rapidly, however the feasibility and safety profile of these interventions for lesions that require real time radiological image-guidance remains unknown. Methods: Patients who underwent IT injections of immunotherapeutic agents across several clinical trials over a 5 year period at a single tertiary cancer center were included in this analysis. Technical success & procedure related adverse events of the IT injection and the frequently accompanying concomitant or sequential image-guided biopsy of injected (adscopal) and non-injected (abscopal) sites were analyzed. Results: A total of 256 patients with metastatic &/or unresectable solid malignancies underwent a total of 1096 (median 5) image-guided IT investigational agent injections during the study period. There were no adverse events attributable to the technical component of the procedure, specifically during the needle insertions or 3862 concomitant biopsies. Soft tissue and nodal lesions in the extraparietal locations & visceral lesions in deeper, intraparietal locations and solid organs were also injected (adrenal, liver and lung). The median injected lesion tumor length was 3.3cm. Serious adverse events (NCI CTC AE ≥ 3) including dyspnea and severe flu-like symptoms developing within 24 hours of the injection & required hospitalization following 1.5% of injections. Conclusions: Intratumoral immunotherapeutic injections & tissue sampling with real time radiological image guidance are feasible across a wide range of regions and organs irrespective of agent and histology. Post-delivery anticipated & adverse events were rare & manageable.

A phase Ib study of endogenous SLC45A2-specific cytotoxic T cells for the treatment of patients with metastatic uveal melanoma

TPS10086

Background: Overall survival (OS) for patients (pts) with advanced uveal melanoma (UM) is poor with a median survival of approximately 12 months. Roughly half of all pts with UM will develop distant metastatic disease despite effective treatment of the primary site. Metastatic UM has a 90% prevalence of liver involvement. Currently, there are no specific FDA-approved treatments for metastatic UM and consensus guidelines recommend participation in a clinical trial. Modern treatments such as checkpoint inhibitors and targeted therapy have less impressive outcomes in UM. Our group has identified peptide epitopes of SLC45A2, a melanosomal transport protein, that is highly expressed in UM and present at very low levels in normal melanocytes. We demonstrated that cytotoxic T cells against SLC45A2 were able to kill HLA-matched UM cell lines. Through the use of enabling technologies, SLC45A2-specific cytotoxic T cells can be isolated and expanded ex-vivo from peripheral blood for use in endogenous T cell (ETC) therapy (a form of adoptive cellular therapy). These activated ETCs can then be infused to traffic to tumor sites. CTLA4 is a T-cell surface protein that binds to B7 with a higher affinity than the costimulatory receptor CD28, providing an inhibitory signal to T-cells. Anti-CTLA4 blockade can divert this inhibition and release the brake on antigen-specific T-cell activation of ETC. We hypothesize that antigen-specific ETCs infused via hepatic artery will be safe and tolerable for UM pts with liver metastasis. Methods: We are conducting a first-in-human clinical trial (NCT03068624 ) of ETC therapy targeting SLC45A2 in combination with anti-CTLA4 in pts with metastatic UM. Pts who express HLA-A*02:01 or A*24:02 undergo apheresis to collect T cells. Their cells then undergo ex vivo cloning and interleukin-21 primed expansion. Hepatic arterial infusion of ETCs will ensure direct localization to the target organ of interest. Conditioning with low-dose cyclophosphamide (300 mg/m2) occurs on Day -2. Hepatic arterial infusion of ETCs on Day 0 is followed by low dose subcutaneous interleukin-2 (IL-2) twice daily for 14 days. The initial dose escalation phase is a 3+3 design with a starting dose level of 3.3 x 109 cells/m2 of ETCs alone. Once the maximum tolerated dose of ETCs is established, the dose expansion phase will include ETCs in combination with anti-CTLA4 (Ipilimumab). The primary objective is to evaluate the safety of this first in human T cell regimen. Secondary objectives are to evaluate the in vivo persistence and anti-tumor efficacy. Clinical trial information: NCT03068624.

S1801: A randomized phase II trial of adjuvant versus neoadjuvant pembrolizumab (PEM) for melanoma

TPS10090

Background: Although long term outcomes for most patients with early-stage melanoma is excellent following surgery, patients who have high-risk features such as lymph node involvement have poorer outcomes. Adjuvant therapy (AT) is currently considered for patients with stage III melanoma and selected patients with resected stage IV melanoma. Currently, AT for melanoma is anti-PD-1 or targeted therapy in the presence of a BRAF mutation. At this time we are not able to predict which patients will derive benefit from AT and experience cure. While curative surgery is the goal of early treatment of primary melanoma, some cases with bulky nodal involvement are at high risk of local or distant recurrence despite upfront surgery. Neoadjuvant treatment (NAT) offers the benefit of an early on-treatment pathological sample that can be profiled for biomarkers and correlated with survival. Treating with anti-PD1 while tumor transiently remains in the body may generate a stronger immune response from tumor-infiltrating lymphocytes against in vivo tumor antigens compared to the traditional adjuvant setting where antigen is presented by microscopic residual tumor burden. Pilot studies using NAT with have been initiated in melanoma. Multidisciplinary coordination in these cases is paramount. In these studies, an improvement in relapse-free survival and overall survival has been observed; additionally, pathologic response rates to NAT have been estimated in small studies. Methods: S1801 is a randomized phase II study of AT versus NAT with PEM (NCT03698019). Patients with measurable, clinically detectable and resectable cutaneous, acral, and mucosal melanomas without brain metastasis are eligible. Patients are randomized 1:1 to the AT or the NAT. Patients getting AT receive surgery first followed by 18 doses of PEM 200 mg IV every 3 weeks. Patients getting NAT receive 3 doses of pre-operative PEM followed by surgery and then 15 doses of adjuvant PEM. Radiation may be given on either arm after surgery, at the investigator’s discretion. Primary endpoint is event-free survival measured from the date of randomization to the date of first documented progression that renders the patient unable to receive planned protocol surgery, failure to begin AT within 84 days of surgery, relapse after surgery, or death due to any cause. Safety monitoring is conducted with disease progression and toxicity thresholds. The key Translational Medicine objective of this trial is to determine the pathologic response rate to NAT with 3 doses of PEM. Enrollment is at 94 of a planned 500 patients. Clinical trial information: NCT03698019.

Melanoma recurrence after adjuvant targeted therapy: A multicenter analysis

10016

Background: Adjuvant targeted therapy (TT) improves relapse free survival (RFS) in patients (pts) with BRAF mutant stage 3 melanoma. The outcomes and optimal management of pts who relapse after adjuvant TT is unknown. Methods: Pts from 21 centres with recurrent melanoma after adjuvant TT were included. Disease characteristics, adjuvant therapy, recurrence, treatment at relapse and outcomes were examined. Results: 87 pts developed recurrent melanoma; 21 (24%) during and 66 (76%) after cessation of adjuvant TT. Median time to 1st recurrence was 16.3 months with median follow up after 1st recurrence of 31 months. 30 (34%) pts recurred locoregionally, 51 (59%) pts developed distant recurrence and 6 (7%) pts had both. Of those who recurred locoregionally, 23/30 (77%) pts underwent surgery to no evidence of disease, only 3 (13%) of which received adjuvant anti-PD1 therapy, and 15/30 (50%) subsequently developed distant disease. 29 (33.3%) pts have died. 75 (86%) pts received systemic therapy at either 1st or subsequent recurrence. 40 (46%) pts received 1st line anti-PD1 based therapy (single agent anti-PD1, anti-PD1 with ipilimumab or anti-PD1 with investigational agent), 12 (14%) pts received ipilimumab monotherapy, 18 (21%) pts received retreatment with combination BRAF/MEK inhibitors and 5 (6%) pts received other agents (chemotherapy, TVEC). 57 (66%) pts had disease that was assessable for response rate (RR). RR after relapse was 69.7% (23/33) to 1st line anti-PD-1 based therapy, 46% (6/13) to TT and 9% (1/11) to ipilimumab monotherapy (Table). Median overall survival (OS) from date of 1st recurrence for all pts was not reached. OS varied by drug class received as 1st line systemic therapy after relapse. 3 year OS was 79% for anti-PD-1 based therapy, 55% for TT and 25% for ipilimumab. Conclusions: This study demonstrates that pts who relapse after adjuvant TT may respond to subsequent immunotherapy at similar rates to the treatment naïve setting. [Table: see text]

Successful tumor-infiltrating lymphocyte (TIL) growth from uveal melanoma (UM) using a three-signal (3.0) method

3027

Background: Metastatic UM is a rare cancer with poor response rates to systemic therapy. Adoptive transfer of patient-specific TIL may represent the best strategy for treatment. TIL are harvested from primary or metastatic tumors and initially expanded in culture with high dose IL-2 prior to undergoing rapid expansion protocol and therapeutic administration. Here, we report improved rates of initial expansion using a previously described TIL 3.0 method which utilizes dual agonistic antibodies to TCR and 4-1BB (Urelumab) for stimulation, respectively, with high dose IL-2, compared to the traditional method. Methods: Between 2006 and 2019, patients were consented for TIL harvest from either primary or metastatic UM tumors. Demographics, clinical features, and outcomes of the TIL initial expansion were collected. Success rates, number of cells expanded, and days in culture for the two methods were analyzed using partially overlapping samples t-tests and z-tests. Results: There were 85 harvests and expansions from 76 patients using the traditional method and 32 expansions from 30 patients using TIL 3.0. Initial TIL expansion was successful in 97% of TIL 3.0 harvests compared to 35% for the traditional method (p < 0.001). More TIL were expanded with TIL 3.0 compared to the traditional method (291.3 million cells vs. 88.6 million cells, p < 0.001), and fewer days were required in culture (18.5 vs. 29.0, p < 0.001). Both primary UM harvests and metastatic harvests were more successful with TIL 3.0 (90% vs. 12% for primary, p < 0.001, and 100% vs. 42% for metastatic, p < 0.001). Conclusions: Expansion of UM tumors via the TIL 3.0 method led to successful growth in 97% of harvests. Therapeutic administration to patients with TIL 3.0 is under active investigation. [Table: see text]

Voluntary exercise may activate components of pro-survival risk pathway in the rat heart and potentially modify cell proliferation in the myocardium

Although physical exercise is known to reduce size of infarction, incidence of ventricular arrhythmias, and to improve heart function, molecular mechanisms of this protection are not fully elucidated. We explored the hypothesis that voluntary running, similar to adaptive interventions, such as ischemic or remote preconditioning, may activate components of pro-survival (RISK) pathway and potentially modify cell proliferation. Sprague-Dawley adult male rats freely exercised for 23 days in cages equipped with running wheels, while sedentary controls were housed in standard cages. After 23 days, left ventricular (LV) myocardial tissue samples were collected for the detection of expression and activation of RISK proteins (WB). The day before, a marker of cell proliferation 5-bromo-2'-deoxyuridine (BrdU) was given to all animals to detect its incorporation into DNA of the LV cells (ELISA). Running increased phosphorylation (activation) of Akt, as well as the levels of PKC? and phospho-ERK1/2, whereas BrdU incorporation into DNA was unchanged. In contrast, exercise promoted pro-apoptotic signaling - enhanced Bax/Bcl-2 ratio and activation of GSK-3ß kinase. Results suggest that in the rat myocardium adapted to physical load, natural cardioprotective processes associated with physiological hypertrophy are stimulated, while cell proliferation is not modified. Up-regulation of pro-apoptotic markers indicates potential induction of cell death mechanisms that might lead to maladaptation in the long-term.

Incidence, patterns of progression, and outcomes of preexisting and newly discovered brain metastases during treatment with anti-PD-1 in patients with metastatic melanoma

BACKGROUND

Melanoma brain metastases (MBM) occur in up to 50% of patients with metastatic melanoma (MM) and represent a frequent site of systemic treatment failure for targeted therapies. However, to the authors' knowledge, little is known regarding the incidence, patterns of disease progression, and outcomes of MBM in patients treated with anti-PD-1 immunotherapy.

METHODS

A total of 320 patients with MM who were treated with anti-PD-1 at The University of Texas MD Anderson Cancer Center in Houston were reviewed. Analyses were performed to identify factors associated with brain metastasis-free survival and overall survival (OS) using Cox regression models.

RESULTS

The median age of the patients was 63.3 years. OS from the initiation of anti-PD-1 therapy was not significantly different between patients without MBM prior to anti-PD-1 compared with patients with prior MBM (P = .359). Among patients without prior MBM, 21 patients (8.6%) developed MBM during anti-PD-1 therapy, 12 of whom (4.9%) presented with disease progression in the central nervous system (CNS) only. Developing MBM during or after therapy with anti-PD-1 (hazard ratio, 4.70; 95% CI, 3.18-6.93) was associated with shorter OS. Among patients with MBM prior to anti-PD-1 treatment, 15 (20.0%) progressed in the CNS only and 19 (25.3%) progressed both intracranially and extracranially; at the time of the last data cutoff, 27 patients (36.0%) had not developed disease progression. Radiation necrosis occurred in 11.3% of patients (7 of 62 patients) in the group with a prior MBM who received stereotactic radiosurgery.

CONCLUSIONS

Anti-PD-1 therapy may change the natural history of patients with preexisting MBM. However, CNS failure during treatment with anti-PD-1 is predictive of a worse prognosis compared with extracranial progression. The results of the current study support the activity of anti-PD-1 in patients with MBM, although routine CNS imaging during therapy is warranted.

A multicenter analysis of melanoma recurrence following adjuvant anti-PD1 therapy

9502

Background: Adjuvant anti-PD1 monoclonal antibodies (mAbs) prolong recurrence-free survival in high-risk resected melanoma, however patients (pts) recur during or after therapy. The patterns of recurrence and optimal management are unclear. Methods: Pts from 15 melanoma centres who recurred having received adjuvant anti-PD1 mAbs (adj-PD1) for resected stage III/IV cutaneous melanoma were included. Disease characteristics, adjuvant treatment, recurrence characteristics, subsequent management and outcomes were examined. Results: 137 pts had melanoma recurrence; 97 (71%) during adj-PD1 and 40 (29%) following treatment cessation (25 had stopped early for toxicity after a median 3 months, 14 after completing 12 months, 1 who withdrew consent after 1 month). Median time to recurrence from start of anti-PD1 was 4.6 months (IQR 2.7-8.5), and median follow up from recurrence was 7.7 months (IQR 3.8-12.3). At 1st recurrence, 78 (57%) pts had distant disease (including 22 with both locoregional and distant), 59 (43%) had locoregional disease only. Of those who recurred locally, 22/59 (37%) later developed distant disease. 26 (19%) pts have died. 81 (59%) pts had systemic therapy for distant recurrence (either 1st recurrence or subsequent). Of those who recurred during adj-PD1, no pts (0/20) subsequently responded to anti-PD1 alone (N = 8) or with any investigational agent (N = 12; anti-LAG3, IDOi, MEKi, TLR9 agonist); 9/27 evaluable pts (33%) responded to ipilimumab-based therapy (alone or in combination with anti-PD1), and 15/19 (79%) responded to BRAF/MEKi . Of those who recurred after ceasing adj-PD1, 2/5 (40%) responded to anti-PD1 monotherapy, 2/5 (40%) responded to ipilimumab-based therapy, 7/8 (88%) responded to BRAF/MEKi. Conclusions: These data suggest minimal activity of further anti-PD1 monotherapy in those who recur while on adj-PD1, but possible activity in those who recur off treatment. Anti-CTLA4 and BRAF/MEKi therapy appear active in those who recur on or following adj-PD1. Data on locoregional recurrence and its management will also be presented.

Lymphodepletion (LD), tumor-infiltrating lymphocytes (TIL) and high (HD-IL2) versus low-dose (LD-IL2) IL-2 followed by pembrolizumab (pembro) in patients (pts) with metastatic melanoma (MM)

9543

Background: TIL adoptive cell transfer (ACT) therapy can produce durable responses for MM pts although efficacy appears lower in the era of checkpoint inhibitors. Toxicities from HD-IL2, including sepsis physiology, limits widespread use of this regimen. Suppression of transferred TIL by either tumor cells or the tumor microenvironment could limit TIL responses. Pembro is known to promote T cell activation, thus, we evaluated the efficacy and safety of TIL with pembro with HD-IL2 versus LD-IL2. Methods: Pts with MM who had tumor harvested and cryopreserved TIL at MD Anderson with PS 0-1 and normal organ function were eligible. All pts received a standard LD regimen consisting of cyclophosphamide and fludarabine, followed by infusion of pooled ex-vivo expanded TIL and either HD-IL2 (Arm 1: 720,000 IU/kg IV q 8 hrs up to 15 doses) or LD-IL2 (Arm 2: 2 million IU SC for 14 d). Pts received pembro 200mg IV starting 21 d post T cell infusion every 3 wks for up to 2 yrs. Pts were randomized 1:1 based on stage and LDH. Paired blood and tumor biopsies were obtained prior to LD, prior to first and second dose of pembro and at time of progression. Results: A total of 36 pts were planned to enroll (18 in each arm); however, the protocol met pre-specified futility boundaries in Arm 1 which prompted early closure after treatment of 14 pts (7 in each Arm). Median age was 50 yrs, 6 were female, 8 had cutaneous melanoma, 2 mucosal, 2 uveal and 2 unknown primary. 86% were stage M1c, 14% M1D, 50% had LDH elevation. Median lines of prior therapy were 3 (range 1-6), including prior anti PD-1 in 13 pts. Best overall response was 1 PR (for 10 mos), 2 SD, 3 PD, 1 NE in Arm 1; 1 PR (ongoing over 36 mos), 1 SD, 5 PD in Arm 2. With median follow up of 9.2 mos, PFS was 3.9 mos for Arm 1 and 2.1 mos for Arm 2 (p = 0.99). Median OS was 9.7 mos for Arm 1 and 8.8 mos for Arm 2 (p = 0.71). Toxicity was similar in both Arms but with lower rates of grade 3 febrile neutropenia (57% vs. 71%) and shorter hospital stay (median 16 vs. 18 d) in Arm 2 vs. Arm 1. Conclusions: In a heavily treated pt population, TIL with pembro achieved low response rates. Use of LD-IL2 did not diminish efficacy and may be better tolerated than HD-IL2 for TIL ACT. Correlative studies are ongoing to determine mechanisms of treatment response and failure. Clinical trial information: NCT02500576.

Phase II single-arm multicenter study of adjuvant ipilimumab in combination with nivolumab in subjects with high-risk ocular melanoma

TPS9604

Background: Treatment of primary ocular melanoma is often very effective, with local recurrence rates of < 5%. However, distant recurrence is as high as 50% depending on features of the primary tumor. These data emphasize the need for effective adjuvant therapy for patients with locally treated ocular melanoma. Several adjuvant treatments have been developed for patients with high-risk cutaneous melanoma, including ipilimumab and nivolumab monotherapies and an ongoing trial is exploring the nivolumab/ipilimumab combination (CA209-915), but patients with high-risk ocular melanomas have been excluded from these trials. As yet there is no approved adjuvant treatment for high-risk ocular melanoma patients. Methods: We are conducting a Phase II single-arm multi-center study of adjuvant ipilimumab in combination with nivolumab in subjects with high-risk ocular melanoma. This study aims to generate efficacy and safety data for adjuvant this regimen in patients with locally treated high-risk ocular melanoma with 3-year risk of relapse > 50%. The primary endpoint is 3-year relapse-free survival rate. Secondary endpoints are median relapse-free survival, median overall survival, 3-year overall survival rate and safety. All patients will receive nivolumab 240mg IV every 2 weeks plus ipilimumab 1mg/kg IV every 6 weeks. Subjects may receive up to 25 doses of nivolumab and 8 doses of ipilimumab. The accrual goal is 50 patients across all participating institutions. Subjects treated in this study will be matched with controls selected from a contemporaneously collected OM registry, “contemporaneous control” in order to better assess efficacy. Control subjects will be from institutions not participating in this trial, will otherwise meet the trial eligibility criteria and will be further matched with trial participants for various demographic and risk factors to the extent possible. The study is enrolling in 6 comprehensive cancer centers in the US. Clinical trial information: NCT03528408.

Cell-free DNA in uveal melanoma: Results from the first-in-human trial of mivebresib (ABBV-075)

e14526

Background: Uveal melanoma (UM) is the most common primary intraocular malignancy in adults. Cell free DNA (cfDNA) is a non-invasive mechanism for monitoring malignancy in UM patients. BET proteins activate transcription of oncogenic genes, and mivebresib (ABBV-075) is a potent pan-BET inhibitor. In the first-in-human phase 1 study, safety and pharmacokinetics of mivebresib were assessed in patients with advanced cancer (NCT02391480). We compared cfDNA mutational dynamics with the survival of UM patients treated with mivebresib. Methods: Adult patients with metastatic solid tumors and ≥1 line of prior treatment were treated with mivebresib on a schedule of daily; 3 days/week; or 4 days on, 3 days off. Two mL of plasma cfDNA (≥10ng) in 5 patients (3 progressive disease [PD], 2 stable disease [SD]) were sequenced with a targeted 63-gene panel (68 Kb) to ≥800X unique depth after barcode-based error-suppression and genomic alterations discovered in all patients. Results: As of May 2018, 10 UM patients received ≥1 dose of mivebresib with median 8.1 weeks (range, 3.6–39.6) of treatment. The median age was 55 years (range, 37–73). 9 patients experienced a treatment-emergent adverse event (TEAE), most commonly (≥40% patient incidence), dysgeusia (60%), thrombocytopenia and nausea (40%, each). 9 patients were evaluable, 4 achieved a best response of SD and 5 PD (RECIST v1.1). The mean pretreatment cfDNA concentration was 21.0 ng/mL (N = 5 with plasma available). cfDNA levels increased in two patients by 0.6% (SD) and 64.4% (PD). In PD patients, elevated cfDNA concentration (32.7 ng/mL [PD] vs 3.5 ng/mL [SD]) was associated with shorter progression-free survival and overall survival. At baseline, the cfDNA mutational load (median mutant molecules/mL plasma) of pathogenic (COSMIC) mutations with AF ≥1% was highest in PD (893.9; range, 78-4951.5) vs SD patients (53.1; range, 9.3-606.2) and negatively correlated with the patient’s survival (R2= 0.531). In 1 PD patient, multiple TP53 (C23G, V203M) and CDKN2A (A148T, L63P) mutations were acquired by the time of progression. Conclusions: These data suggest cfDNA as a potential marker for survival of UM patients. Further investigation of BET inhibition in this population is warranted. Clinical trial information: NCT02391480.

A phase II study of oral azacitidine (CC-486) in combination with pembrolizumab (PEMBRO) in patients (pts) with metastatic melanoma (MM)

9560

Background: Immune checkpoint blockade (ICB) have improved survival for many pts with MM, offering durable responses in up to 35% of pts, but many have short-lived or no response ( > 40%). A potential immune escape mechanism is the subversion of cellular epigenetic machinery to impact multiple aspects of the immune response such as suppression of Cancer Testis Antigen (CTA), which can be reversed in preclinical models by DNA hypomethylating agents (HMA), thereby increasing cancer cell immunogenicity. HMAs can also increase T cell infiltration and T cell-mediated tumor killing, and they achieve synergy with CBI in preclinical models. This suggests that epigenetic therapy with CBI is a rational combination to target MM. We hypothesize that CC-486 (an oral HMA) + PEMBRO will be tolerated at biologically relevant doses and enhance response to PEMBRO in pts with MM who are PD-1 naïve and reverse resistance to (ICB) in pts refractory/resistant to PD-1. Methods: This study (NCT02816021) evaluated the safety and efficacy of CC-486 (300 mg PO QD on days 1-14/21 day cycle) + PEMBRO (200mg IV Q 21 days) defined by Objective Response Rate (ORR) by RECIST 1.1 in pts with MM. PD-1 naïve pts were assigned to Arm A and pts with progression on prior PD-1 therapy to Arm B. Unlimited prior systemic therapies were allowed on Arm B. Continuous monitoring for toxicity and futility was performed and assumes an ORR of > 35% (Arm A) and > 15% (Arm B) at 95% power. Tumor biopsies at baseline and post treatment were mandated. Results: 22pts, 11 in each arm, have been treated. The most common AEs were nausea, vomiting, diarrhea, fatigue, and anemia. The most common gr 3/4 toxicities were neutropenia (3), diarrhea (2), dehydration (2), and rectal hemorrhage (1). 5 of 9 evaluable pts in Arm A achieved a PR (55% ORR); 0 of 9 evaluable pts in Arm B pts have responded. Conclusions: Although this regimen was tolerated in both arms, Arm B met futility stopping rules and was closed. The initial response rate in Aim A (55%) is promising, and accrual to this Arm continues. Analyses of longitudinally collected tumor biopsies are underway to interrogate the effects of HMA on the immune response to both arms. Clinical trial information: NCT02816021.

Phase II study of ipilimumab and nivolumab (ipi/nivo) in metastatic uveal melanoma (UM)

9522

Background: UM is the most common primary intraocular malignant tumor in adults. Approximately 40-50% of patients (pts) with UM will ultimately develop metastatic disease. There is currently no standard approach for metastatic UM. Early studies of single agent immunotherapy (IO) in metastatic UM have yielded meager results. Combination checkpoint inhibitor IO has the potential to improve response rates and survival. Herein, we report the safety and efficacy of ipi/nivo in metastatic UM. Methods: We performed a single-arm phase II study in metastatic UM (CA184-187) for pts with at least 1 measureable lesion and ECOG PS 0-1. Any number of prior treatments were permitted. Pts received nivolumab 1mg/kg IV plus ipilimumab 3mg/kg IV every 3 weeks for a total of 4 doses; maintenance nivolumab was dosed 3mg/kg every 2 weeks or 480mg IV every 4 weeks. The primary efficacy endpoint was best overall response rate (BORR) as determined by irRC. Secondary endpoints were median progression free survival (PFS), median overall survival (OS), and one-year OS. Results: As of the January 31, 2019 data cutoff, 39 pts were enrolled. 35 pts received at least one treatment and were evaluable for toxicity. 5 pts were inevaluable for response due to lack of follow-up imaging, leaving 30 pts evaluable for efficacy. 32 pts (91%) experienced any adverse event (AE), and 29 pts (83%) experienced any treatment related AE (TRAE). Grade 3-4 TRAEs occurred in 14 pts (40%). 10 pts (29%) were removed from the study due to AEs. There were no treatment-related deaths. Median duration of follow up is 60.5 weeks. 19 pts (63%) completed all 4 cycles of ipi/nivo; median duration of treatment was 16 weeks. The BORR was partial response for 5 pts (17%), stable disease (SD) for 16 pts (53%), and progression of disease for 9 pts (30%). 8 pts had SD for at least 6 months. Median PFS was 26 weeks. Median OS was 83 weeks (1.6 years), and one-year OS was 62%. Conclusions: Full results of ipi/nivo safety and efficacy including immune-related AE and clinical characteristics of the responders will be presented at the meeting. Preliminary translational tumor work including RNA analysis has been performed on a subset of responders. Clinical trial information: NCT01585194.

Hypoxia-Driven Immunosuppressive Metabolites in the Tumor Microenvironment: New Approaches for Combinational Immunotherapy

Hypoxia is not only a prominent contributor to the heterogeneity of solid tumors but also a crucial stressor in the microenvironment to drive adaptations for tumors to evade immunosurveillance. Herein, we discuss the potential role of hypoxia within the microenvironment contributing to immune resistance and immune suppression of tumor cells. We outline recent discoveries of hypoxia-driven adaptive mechanisms that diminish immune cell response via skewing the expression of important immune checkpoint molecules (e.g., cluster of differentiation 47, programmed death ligand 1, and human leukocyte antigen G), altered metabolism and metabolites, and pH regulation. Importantly, inhibition of hypoxic stress-relevant pathways can collectively enhance T-cell-mediated tumor cell killing. Furthermore, we discuss how manipulation of hypoxia stress may pose a promising new strategy for a combinational therapeutic intervention to enhance immunotherapy of solid tumors.

Gut microbiome modulates response to anti-PD-1 immunotherapy in melanoma patients

Preclinical mouse models suggest that the gut microbiome modulates tumor response to checkpoint blockade immunotherapy; however, this has not been well-characterized in human cancer patients. Here we examined the oral and gut microbiome of melanoma patients undergoing anti-programmed cell death 1 protein (PD-1) immunotherapy (n = 112). Significant differences were observed in the diversity and composition of the patient gut microbiome of responders versus nonresponders. Analysis of patient fecal microbiome samples (n = 43, 30 responders, 13 nonresponders) showed significantly higher alpha diversity (P < 0.01) and relative abundance of bacteria of the Ruminococcaceae family (P < 0.01) in responding patients. Metagenomic studies revealed functional differences in gut bacteria in responders, including enrichment of anabolic pathways. Immune profiling suggested enhanced systemic and antitumor immunity in responding patients with a favorable gut microbiome as well as in germ-free mice receiving fecal transplants from responding patients. Together, these data have important implications for the treatment of melanoma patients with immune checkpoint inhibitors.

Prognostic factors for overall survival (OS) in metastatic melanoma (MM) patients (pts) treated with immune checkpoint inhibitors: A single institution study of 696 pts

9574

Background: Limited OS data, including prognostic and predictive factors of response, is available in mm pts treated with immune checkpoint inhibitors. Methods: A single-institution retrospective review was conducted on 696 mm pts treated with single-agent anti CTLA-4 or anti PD-1 on and off clinical trial between 2011-2015. Median OS was calculated from mm diagnosis. Results:Median age at mm diagnosis was 60 years old (range 15-86) and 65.2% were male. Subtypes were 63.2% non-acral cutaneous, 17.2% unknown primary, 7.8% mucosal, 6.5% acral, and 5.3% uveal. AJCC v7 staging at diagnosis was 7.9% M1a, 16.5% M1b, 33.0% M1c, and 42.5% not staged due to unknown LDH. LDH was elevated in 18.0% (400 pts). Mutation rates were 30.0% BRAF V600E/K (636 pts tested) and 24.5% NRAS (429 pts tested). First-line therapy for BRAF V600E/K mm pts included anti CTLA-4 (24.1%), BRAF/MEK targeted therapy (21.5%) and anti PD-1 (8.9%). First-line therapy for BRAF WT mm pts included anti CTLA-4 (28.1%) and anti PD-1 (12.8%). Median OS from mm for the cohort was 36.5 months (95% CI 33.3-44.9). Elevated LDH and staging correlated with OS (p < 0.001, p < 0.001, respectively) on univariate analysis. Age, gender, subtype and mutation status were not significantly associated with OS. Compared to BRAF WT, pts with BRAF V600E/K mutation were younger (median = 53 vs 62 yrs, p < 0.001), more likely to have non-acral cutaneous mm (83.2% vs 58.0%, p < 0.001) and have a diagnosis of brain metastasis during the disease course (57.0% vs 28.8%, p < 0.001). While adjusting for stage, there was no significant difference in OS based on first or second line therapy in pts with BRAF V600E/K mm or first line therapy in BRAF WT MM; however, BRAF WT pts treated second line with anti-PD1 were observed to have improved OS compared with pts receiving anti-CTLA 4 (HR 0.43 95% CI:0.23-0.84 p = 0.012). Conclusions: This study demonstrates that LDH and stage are prognostic of OS in all mm pts treated with single agent immune therapy. Second line therapy in BRAF WT pts treated with single agent immune therapy is also prognostic of OS thus prompting further investigation to determine advantageous therapy sequencing in MM.

Incidence, patterns of progression and outcomes of melanoma brain metastasis (MBM) during programmed-death 1 inhibitor (PD1i) therapy

9532

Background: MBM are common in patients (pts) with metastatic melanoma (MM) and represent a frequent site of treatment failure with current therapies. Little is known, however, about the incidence, patterns of progression and outcomes of MBM pts treated with PD1i and in conjunction with central nervous system (CNS) focused therapy. Methods: Outcomes of mm pts treated with PD1i at MD Anderson from 01/12 to 07/16 were reviewed. The association between clinical variables and development of MBM and overall survival (OS) were assessed using logistic regression and Cox regression analyses. Results: We identified 324 mm pts, including 77 pts (24%) who had MBM prior to first dose of PD1i. Median follow-up from start of therapy was 16.3 months, median OS for pts without MBM at the start of PD1i 3.37 years, as compared to 2.85 years in pts with prior MBM (p = 0.268). Of the 247 pts without prior MBM, 64 (26%) developed MBM after exposure to PD1i. Of those, 21 pts (8.5%) developed MBM during therapy or within 30 days of discontinuation, with 12 (4.5%) having CNS-only progression, while 9 (3.6%) had both systemic and CNS progression. Pts with MBM prior to PD1i (n = 77) had CNS-only progression in 22 pts (28.6%) during therapy. Progression occurred in systemic and systemic plus CNS in 12 pts (15.6%) and 19 pts (24.7%), respectively. 24 pts (31.2%) had stable disease (SD). On multivariate analysis, pts with lung metastases (OR, 2.16; 95% CI, 1.25 - 3.78; p = 0.006) and NRAS-mutated tumors (OR, 2.17; 95% CI, 1.14 - 4.18; p = 0.02) were more likely to develop MBM; pts who had liver metastases at the start of PD1i (HR, 1.77; 95% CI, 1.09 - 2.87; p = 0.002) and those who developed MBM during PD1i (HR, 4.81; 95% CI, 3.00 - 7.71; p < 0.0001) had increased risk of death. Conclusions: We found a 26% incidence of MBM after PD1i exposure. Pts that develop MBM are still at higher risk of death despite advances in systemic and local CNS therapy. CNS-only progression was substantially higher in patients with MBM prior to PD1i, supporting a change in the natural history of the disease after PD1i. These findings support the use of CNS imaging to monitor disease during PD1i therapy.

Relapse-free survial and target identification to enhance response with neoadjuvant and adjuvant dabrafenib + trametinib (D+T) treatment compared to standard-of-care (SOC) surgery in patients (pts) with high-risk resectable BRAF-mutant metastatic melanoma

9587

Background: Targeted and immune therapies have dramatically improved outcomes in stage IV metastatic melanoma pts. These agents are now being tested in earlier-stage disease. SOC surgery for high-risk resectable melanoma (AJCC stage IIIB/IIIC), with or without adjuvant therapy, is associated with a high risk of relapse (~70%). We hypothesized that neoadjuvant (neo) + adjuvant treatment with D+T improves RFS in these pts. Longitudinally collected biospecimens from pts receiving this treatment were analyzed to identify candidate strategies to further improve outcomes. Methods: A prospective single-institution randomized clinical trial (NCT02231775) was conducted in BRAF-mutant pts with resectable Stage IIIB/C or oligometastatic stage IV melanoma. Pts were randomized 1:2 to SOC (Arm A) versus neo + adjuvant D+T (Arm B; 8 wks neo + 44 wks adjuvant). The primary endpoint was RFS. Tumor biopsies were collected at baseline, week 3, and at surgery for molecular and immune profiling (whole exome sequencing, gene expression profiling, IHC, flow cytometry). Results: 21 of a planned 84 patients were enrolled (Arm A = 7, Arm B = 14). Arms were well balanced for standard prognostic factors, and toxicity was manageable. RECIST response rate with neo D+T was 77%, and the pathologic complete response rate (pCR) was 58%. First interim analysis revealed significantly improved RFS in the D+T arm over SOC (HR 62.5, p < 0.0001), leading to early closure to enrollment. Pts with a pCR at surgery had significantly improved RFS versus pts without pCR (p = 0.04) on neo D+T. Tumor profiling revealed incomplete MAPK pathway blockade and higher levels of CD8+ T cells expressing immunomodulators Tim-3 and Lag-3 in pts who did not achieve a pCR. Conclusions: Neo + adjuvant D+T is associated with a high pCR rate and markedly improved RFS over SOC in pts with high-risk resectable BRAF-mutant metastatic melanoma. pCR at surgery is associated with improved RFS. Tumor analyses reveal candidate targets for testing in future trials to enhance responses to neo D+T. Clinical trial information: NCT02231775.

A toll-like receptor agonist to drive melanoma regression as a vaccination adjuvant or by direct tumor application

9582

Background: Toll like receptor (TLR) agonists may enhance vaccination or direct immune activation at the tumor microenvironment. This trial evaluates the biologic and clinical effects of Resiquimod, a TLR 7/8 agonist that can activate both myeloid (mDC, TLR 8) and plasmacytoid (pDC, TLR 7) dendritic cells, in patients with advanced stage melanoma. Methods: Class I HLA-A0201+ subjects with in-transit melanoma metastases or high risk for recurrence were vaccinated weekly with peptide vaccination (class I restricted peptide GP100209-2m and, if HLA-DP4+, also with class II restricted peptide MAGE-3243-258). Subjects were randomized 1:1 to receive Resiquimod as an adjuvant applied to the GP100 vaccination site. Subjects with in-transit disease were thereafter treated with resiquimod topically on half of the target lesions. Results: All patients (n = 47) underwent GP100209-2m vaccination, a majority (39) also received the MAGE-3243-258 peptide. The type I interferon-inducible genes (Mx A and IRF7), IFNg, and IP-10 RNA expression were up-regulated only in vaccination sites treated with Resiquimod (each p < 0.01) , demonstrating pDC activation (Type I interferon) and possibly T and NK cell activation (IFNg and IP-10). Nineteen subjects had in-transit disease at entry into the trial. In response to peptide vaccination alone, tumor regression was more likely in patients who received Resiquimod at the vaccination site (group A) compared to those who did not (group B). (4/9 vs 0/10, p = 0.033). In group A, 5 patients continued treatment with Resiquimod topically on the tumors, and all had tumor response (4PR, 1CR). In group B, 5 continued to tumoral resiquimod and 3 had regression (3 PR). Conclusions: Resiquimod increases Type I interferon and IFNg at the peptide vaccination site by activation of pDC/mDC and increases the antitumor response sufficiently to mediate regression of in-transit melanoma metastasis. Resiquimod on in-transit melanoma, in vaccinated hosts, drives regression of metastases, regardless of previous exposure at vaccination. Clinical trial information: NCT00960752.

The safety and early efficacy of high-dose ipilimumab (IPI) and the combination nivolumab plus ipilimumab (NIVO + IPI) in patients (pts) with uveal melanoma (UM)

9554

Background: UM metastases occur in 50% of cases and high-risk pts are identified by a gene expression profile. High-dose IPI is approved for adjuvant (adj) treatment (tx) of cutaneous melanoma and NIVO + IPI for metastatic (met) melanoma, yet the safety and efficacy of high-dose IPI or NIVO + IPI has not been established in UM in the adj or met settings. Methods: We performed a phase I/II trial of IPI for the tx of high-risk & met UM (CA184-187). The study consisted of two arms: an adj arm (AA) & met arm (MA) with two dose levels, 3 mg/kg & 10 mg/kg. Dose-finding proceeded on each arm in a 3 + 3 fashion. Pts received IPI once every 3 weeks for four doses followed by maintenance IPI every 12 weeks (for up to one year in AA). The AA treated pts with a Class 2 gene expression profile. This score imparts a 3-year distant metastasis-free survival (DMFS) of 50%. The primary endpoint for the AA was maximum tolerated dose (MTD) and improvement in 3-year DMFS to 70%. The primary endpoint for the MA was MTD & overall survival. The study was later amended to include a cohort of UM pts treated with combination NIVO + IPI in the standard FDA approved schedule. Results: Ten pts were enrolled on AA, 18 on MA, and 20 on NIVO + IPI. Adverse events (AEs) of any Grade (Gr) related to tx occurred in 80% of pts on AA. Gr 3/4 related toxicities observed in more than one pt were: transaminitis (30%) & pruritus (20%). Of these, 10% of the elevated AST and ALT and 10% of the pruritus occurred during the dose-finding portion of the trial at 3 mg/kg. One pt developed biopsy-proven colitis, and one developed diarrhea. Both were treated with high-dose steroids. One pt developed vasculitis manifesting as temporal arteritis with resultant blindness. AEs of any Gr occurred in 44% of pts on MA. Gr 3/4 toxicities observed in more than one pt were: Fatigue (11%) and Hyperbilirubinemia (11%). Only 1 pt (5.6%) developed Gr 3/4 diarrhea, and this was at the 3 mg/kg dose. In the NIVO + IPI cohort, Gr 3 transaminitis & elevated TSH occurred in 10%. Conclusions: High-dose IPI in UM did not demonstrate new or unexpected toxicities. Similarly, the combination of NIVO + IPI was well-tolerated with no new toxicities. Efficacy data will be presented at the meeting. Clinical trial information: NCT01585194.