Single-agent anti-PD-1 or combined with ipilimumab in patients with mucosal melanoma: an international, retrospective, cohort study

BACKGROUND

Mucosal melanoma (MM) is a rare melanoma subtype with distinct biology and poor prognosis. Data on the efficacy of immune checkpoint inhibitors (ICIs) is limited. We determined the efficacy of ICIs in MM, analysed by primary site and ethnicity/race.

PATIENTS AND METHODS

Retrospective cohort study from 25 cancer centres in Australia, Europe, USA and Asia. Patients with histologically confirmed MM were treated with anti-PD1+/-ipilimumab. Primary endpoints were response rate (RR), progression-free survival (PFS), overall survival (OS) by primary site (naso-oral, urogenital, anorectal, other), ethnicity/race (Caucasian, Asian, Other) and treatment. Univariate and multivariate Cox proportional hazard model analyses were conducted.

RESULTS

In total, 545 patients were included: 331 (63%) Caucasian, 176 (33%) Asian and 20 (4%) Other. Primary sites included 113 (21%) anorectal, 178 (32%) urogenital, 206 (38%) naso-oral and 45 (8%) other. 348 (64%) received anti-PD1 and 197 (36%) anti-PD1/ipilimumab. RR, PFS and OS did not differ by primary site, ethnicity/race or treatment. RR for naso-oral was numerically higher for anti-PD1/ipilimumab (40%, 95% CI 29-54%) compared with anti-PD1 (29%, 95% CI 21-37%). 35% of patients that initially responded progressed. Median duration of response (mDOR) was 26 months (95% CI 18-NR [Not Reached]). Factors associated with short PFS were ECOG PS ≥3 (p<0.01), LDH >ULN (p=0.01), lung metastases (p<0.01) and ≥1 previous treatments (p<0.01). Factors associated with short OS were ECOG PS ≥1 (p<0.01), LDH >ULN (p=0.03), lung metastases (p<0.01) and ≥1 previous treatments (p<0.01).

CONCLUSIONS

MM has poor prognosis. Treatment efficacy of anti-PD1+/-ipilimumab was similar and did not differ by ethnicity/race. Naso-oral primaries had numerically higher response to anti-PD1/ipilimumab, without difference in survival. The addition of ipilimumab did not show greater benefit over anti-PD1 for other primary sites. In responders, mDOR was short and acquired resistance was common. Other factors, including site and number of metastases were associated with survival.

Real-world evaluation of the association between baseline metastatic patterns and clinical outcomes among patients with BRAF-positive metastatic melanoma

9532

Background: While immunotherapy (IO) and BRAF-targeted therapy (TT) have benefit in BRAFV600 mutant (BRAF+) metastatic melanoma (MM), there is a paucity of real-world data on the impact of systemic therapy choice on outcomes based on key characteristics such as site and number of baseline metastases. Patients with >1 baseline site and certain sites of metastases are also underrepresented or excluded in clinical trials. The aim of this study was to evaluate the association between these characteristics and survival among BRAF+ MM patients. Methods: This was a retrospective cohort study using the Novartis BRAF+ meLanoma patients ObsErvational (NOBLE) dataset – harmonized customized data from Flatiron and ConcertAI. It included patients ≥18 years, who received treatment with a first-line (1L) IO (anti-PD-1 mono or combination therapy ipilimumab + nivolumab) or TT (any BRAF/MEK-inhibitors) after 1/1/2014. Progression free survival (PFS) and overall survival (OS) for IO and TT were analyzed according to number (1, 2, 3+ sites) and location (brain, lung, liver, bone) of baseline metastasis. Treatment sequence from 1L to 2L (i.e. IO/TT vs TT/IO) were also compared for PFS and OS outcomes. Results: A total of 1,961 patients were included, with 620 patients (32%) on IO monotherapy, 501 patients (26%) on IO combo therapy, and 840 patients (43%) on TT in the 1L. When adjusted for sex, age, ECOG, and Charlson Comorbidity Index, there was no difference in PFS or OS between 1L IO mono, IO combo and TT therapies in patients who had 1, 2, or 3+ baseline metastases. For patients who had either baseline brain, liver, lung, or bone metastasis, there was no difference in PFS and OS between IO mono, IO combo, and TT combo therapies. Of the 521 patients included in the sequencing analysis (only patients who received 2L therapy), 239 patients (46%) had 1L IO/2L TT. There was no difference in PFS or OS between treatment sequences for patients with any number or location of baseline metastasis. Conclusions: In this real-world retrospective cohort study, there is no difference in survival between 1L TT and IO for BRAF+ MM patients. Outcomes are comparable regardless of number and location of metastases, including brain metastasis. Whether switching from 1L TT to IO before progression may account for differences compared to trial data will be explored further.[Table: see text]

Evaluation of the use of COVID-19 vaccines in patients treated with immunotherapy

e18781

Background: Immunotherapy can boost a patient’s immune system to bring about anti-tumor activity and may theoretically exaggerate the inflammatory immune response to infection or vaccinations. Conversely, vaccination may enhance immune activity in patients on immunotherapy. Currently, there are limited safety data in patients treated with immunotherapy who received COVID-19 vaccines. Methods: An IRB-approved retrospective review of Dana-Farber Cancer Institute patients treated with PD-1 checkpoint inhibitors and received COVID-19 vaccines was performed. The primary endpoint was the incidence rate of immune-related adverse events (irAEs) pre- and post- COVID-19 vaccinations. An Electronic Health Record search identified all patients who completed COVID-19 vaccines between 12/1/2020 and 3/31/2021 and received anti-PD-1 monotherapy between 10/1/2020 and 5/31/2021. Medical record review identified timing, occurrence, and grading of irAEs as defined by clinicians or Common Terminology Criteria for Adverse Events (CTCAE), version 5.0. Results: A total of 229 patients were included in the study. The most common underlying cancers were lung (32%) and melanoma (26%). The majority of patients had Pfizer-BioNTech COVID-19 vaccine; 64% of all patients received the third dose of vaccine. The median duration of treatment was 15 months, and median duration of follow-up was 19 months. Among the study cohort, 120 irAEs occurred before vaccination (any grade); 30 (25%) were grade 1, 35 (29%) were grade 2, 11 (9%) were grade 3 or 4, and 44 (37%) were ungraded. The main types of irAEs were skin toxicities (37% of all irAEs) followed by thyroid dysfunction (22%) and colitis (11%). Of the 75 irAEs that occurred after vaccination, 24 (32%) were grade 1, 16 (21%) were grade 2, 16 (21%) were grade 3 or 4, and 19 (26%) were ungraded. The main irAEs types were skin toxicity (31% of all irAEs) followed by thyroid dysfunction (13%) and hepatic toxicity (12 %). The all-grade pre- and post-vaccine irAE incidence rates per 100 patient-months were 4.13 and 5.09, respectively. Within this cohort, there were 0.96 (95% CI -0.362-2.284, p = 0.15) more irAEs post vaccine per 100 patient-months of anti-PD-1 therapy. Conclusions: The data weakly suggested that there is a higher incidence of irAEs post COVID-19 vaccine; however, the comparison did not achieve statistical significance. Further analysis of other patient characteristics will help to determine if any specific patterns are observed.[Table: see text]

Thromboembolism (TE) and association with survival in patients (pts) with melanoma receiving chemo– or immunotherapy

12082

Background: Emerging reports suggest high rates of venous thromboembolism (VTE) and arterial thromboembolism (ATE) with immune checkpoint inhibitors (ICI) in pts with melanoma, but it is unclear whether these are truly increased compared to older systemic therapy approaches. We assessed the incidence of TE in melanoma pts on ICI, cytokine therapy (CY), and chemotherapy (chemo), and evaluated its impact on survival. Methods: We conducted a cohort study using the SEER-Medicare database to evaluate rates of TE in pts with melanoma treated from 2008-2019 with ICI (ipilimumab, nivolumab, pembrolizumab), CY (IL2, IFN), and/or chemo (antineoplastic agents, BRAF/MEK inhibitors) within two years of treatment initiation. TE including VTE events of deep venous thrombosis, pulmonary embolism, and ATE of MI, ischemic stroke, and transient ischemic attack were identified by at least two outpatient claims or one inpatient claim. Overall survival (OS) from treatment start was analyzed by time-varying Cox analysis. Results: The cohort comprised 13,124 pts with median age 75 (24-101) years and 68% male. Of these, 14.8% received ICI, 48.9% chemo, 1.7% CY, 31.8% chemo+ICI, and 2.8% chemo+CY. At treatment start, comorbidities included 72% of pts with hypertension, 33% cerebrovascular disease, 17% atrial fibrillation, 7.3% history of VTE, and 13.0% history of ATE. Overall, 11.4% were on anticoagulation and 5.2% on antiplatelet agents. Incidence rates of ATE and VTE after treatment start are shown (Table). VTE was highest at 3 months after starting therapy with 19.6 events per 100 person-years in those receiving chemo+ICI, 17.1 events with chemo, 15.4 events with ICI, 10.1 events with chemo+CY, and 7.7 events with CY. In multivariable analysis, VTE and ATE were associated with worse OS compared to patients without (HR 2.77 [95%CI, 2.50-3.08], and HR 2.53 [95%CI, 2.23-2.86], respectively). Conclusions: Systemic therapy with ICI and chemo, especially when exposed to both sequentially or concurrently, demonstrates a high incidence of TE in pts with melanoma. TE is associated with substantial worsening of survival. TE rates are not substantially increased with ICI in comparison to chemo. Further studies are needed to identify benefit of thromboprophylaxis.[Table: see text]

Characterizing the tumor and immune landscape of melanoma patients treated with combined checkpoint blockade and MAPK targeted therapy

9522

Background: Melanoma therapy has been revolutionized by two novel therapeutic approaches: mitogen activated protein kinase (MAPK) targeted therapy (MTT) and immune checkpoint blockade therapy (ICB). Less than half of patients respond to ICB monotherapy, in part due to non-responsive tumor microenvironment (TME). It previously has been shown that MTT enhances anti-tumor immunity within the TME, thus providing a strong rationale for its combination with immunotherapy. Regimens combining MTT with ICB have had mixed results, and which patients should be treated with these combinations is unknown. Methods: The first arm (NCT03149029) of a planned two stage design was to enroll 14 patients (pts) harboring BRAFV600 mutation treated with 2 weeks (wks) of MTT (dabrafenib plus trametinib) then 6 wks of concomitant MTT and pembrolizumab, followed by single-agent pembrolizumab thereafter. The primary endpoint is clinical benefit (CB) defined as partial/complete response or stable disease (per RECIST1.1) persisting at 24 wks. If 9 of 14 pts had CB, then 11 more pts would be enrolled for a total cohort of 25. Serial biopsies were performed prior to MTT, following the 2-week lead-in of MTT, and following six wks of combination immune therapy and MTT. Single-cell RNA-seq profiling of CD45+ and CD45- cells was performed using both the smart-seq2 plate-based protocol and 10x genomics platform. Results: Sixteen pts were enrolled, with 14 receiving both MTT and ICB. Two pts did not receive ICB due to MTT toxicity. Only 5 had CB, and the second stage did not open. A 6th pt had CB extracranially with a new small brain met at wk 24 scans was considered CB for tumor analysis. A clustering analysis of 25 samples (n = 9 pts) showed that following MTT the abundance of CD8 T-cells as well as tumor IFNγ levels were significantly elevated in CB vs. no CB (NCB) patients. In addition, tumor associated macrophages (TAM) in NCB patients possessed mainly an M2 phenotype and expressed a significantly higher level of immune suppressor genes, such as HLA-G and CD52. Interestingly, NCB pts had a significantly higher expression of tumor TGFβ, which is a strong inducer of M2 macrophages. In contrast, most of the TAMs occupying the tumor of the CB pts had the M1 phenotype, and significantly expressed CD9, CD81 and CD82, important factors during antigen recognition and immunological synapse formation. Conclusions: Abbreviated MTT with ICB did not lead to increased clinical benefit at 24 wks in this small study. It is theorized that the tumor’s ability to create a unique microenvironment by producing certain factors (e.g. TGFβ), modifies the immune system and may tilt its path into immune suppression thereby reducing the efficacy of this combinatorial therapy in melanoma pts with metastatic disease. These results may help identify pts most likely to benefit from combined MTT plus ICB and new targets to overcome resistance to these regimens. Clinical trial information: NCT03149029.

Pathology of durable stable disease in melanoma patients treated with ipilimumab, nivolumab, or ipilimumab, and nivolumab combination therapy

9567

Background: As immunotherapy with checkpoint blockade becomes the backbone of melanoma treatment there is a need to better understand the biology associated with long term benefit. One particularly interesting set of patients are those with prolonged stable disease or response with residual findings on imaging. It is unknown if immunotherapy has led to scarring at the site of prior disease or if there are residual tumor cells being controlled by an ongoing immune response. Evaluating tissue from patients with prolonged responses provides a unique opportunity to determine the composition of residual lesions. Correlation with PET/CT helps determine if this is an accurate modality to reflect presence of residual viable tumor tissue. Methods: Metastatic melanoma patients that have attained long term stable disease after treatment with ipilimumab, nivolumab, or ipilimumab plus nivolumab were identified. Patients must have received ipilimumab, nivolumab or combination therapy 2+ years prior to enrollment and must have had stable disease for ≥ 6 months. Patients were consented and underwent PET/CT scans and biopsies of residual areas of stable disease. Pre- and post-treatment tissue samples underwent pathologic assessment to look at tumor cell content, fibrotic content, and inflammation. Results: Ten patients were consented for evaluation but only 7 met the screening criteria and underwent PET/CT and tissue biopsy. Six patients had FDG avid lesions on PET/CT which ranged in intensity from SUV 2.4-22. One patient had no FDG avidity in the areas of residual disease observed on CT. Biopsies from the residual stable lesions demonstrated predominantly necrosis and fibrosis with prominent pigment containing macrophages. One patient with an axillary nodal lesion with an SUV of 22 had active melanoma on pathology which was resected, and the patient has subsequently remained without progression of disease. Conclusions: Patients with durable stable disease after treatment with ipilimumab, nivolumab or ipilimumab and nivolumab combination therapy represent a unique population of melanoma patients treated with immune checkpoint inhibition. An examination of the residual lesions observed in these patients demonstrated predominantly necrosis and fibrosis consistent with resolving lesions. The presence of melanophages in these samples may suggest some ongoing immune surveillance. One patient did demonstrate residual melanoma suggesting the need for ongoing monitoring of this patient population.

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.

Trial in progress: Phase 1a/b study of PF-07284890 (brain-penetrant BRAF inhibitor) with/without binimetinib in patients with BRAF V600-mutant solid tumors

TPS3152

Background: BRAF inhibitors have transformed treatment (Tx) for patients (pts) with BRAF V600-mutant cancers, but long-term efficacy is limited by disease progression in the brain, due to poor brain penetration. PF-07284890 is a potent, selective, highly brain-penetrant, small-molecule inhibitor of BRAF V600 mutations. This first in human study will assess the PK, safety, and preliminary clinical activity of PF-07284890, as monotherapy and in combination with binimetinib (MEK inhibitor), in pts with BRAF V600-mutated advanced solid tumors with/without brain metastases. Methods: Phase 1a/1b open-label, multicenter, dose-finding study (NCT04543188). Pts will be ≥18 y with a histologically confirmed advanced/metastatic solid tumor including primary brain tumor (PBT), confirmed BRAF V600 mutation, and presence/absence of brain involvement. Pts will have disease progression despite prior Tx without alternative Tx options. Pts with brain metastasis/PBT > 4 cm and/or symptomatic brain disease will be excluded initially, but allowed based on emerging PK. Phase 1a is a dose escalation study of PF-07284890 (monotherapy and combination). ̃35 pts will be enrolled to determine maximum tolerated dose (MTD) and/or recommended dose for expansion (RDE) of PF-07284890 (monotherapy and combination). Cohorts of 2-4 pts will be treated at each dose level of PF-07284890 until MTD/RDE determination (PF-07284890 starting dose: 50 mg QD; binimetinib 45 mg BID). Bayesian Logistic Regression Model will be used to inform dose level decisions. At least 6 pts each for monotherapy and combination will be treated at MTD/RDE. Phase 1a primary endpoints: Cycle 1 dose-limiting toxicities; MTD/RDE; AEs; lab abnormalities; and dose interruptions, modifications and discontinuations due to AEs. Secondary endpoints include PK parameters and overall response (RECIST; overall and intracranial; RANO for PBT). Phase 1b is a dose expansion and drug-drug interaction study to further evaluate PF-07284890 + binimetinib. Cohorts 1-4 (̃40 pts each) will enroll pts based on tumor type, brain involvement (asymptomatic/symptomatic), and prior Tx. Cohort 5 (̃20 pts) will include pts with any solid tumor including leptomeningeal metastases. Cohort 6 (̃10 pts) will assess the effect of PF-07284890 + binimetinib on CYP3A activity using midazolam as a substrate. Phase 1b primary endpoint: overall response (RECIST; overall and intracranial; RANO for PBT). Secondary endpoints: duration of response; progression-free survival; disease control rate; time to response; overall survival; AEs; lab abnormalities; and dose interruptions, modifications and discontinuations due to AEs; and PK parameters. For both Phase 1a and 1b, Tx will continue until disease progression, unacceptable toxicity or patient refusal. Study began enrolling pts in January 2021 and is ongoing. Clinical trial information: NCT04543188.

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.

A phase 1, open-label, dose escalation study of the safety and tolerability of T3011 in advanced cutaneous or subcutaneous malignancies

2526

Background: T3011 is a genetically modified, next-generation oncolytic HSV-1 with 2 exogenous genes encoding the active heterodimer human interleukin 12 (IL-12) and the Fab fragment of an anti-human PD-1 antibody. Locally produced IL-12 induces the synthesis of interferon-gamma (IFN-γ) production, enhancing cytolytic activity of natural killer cells and cytotoxic T lymphocytes. The anti PD-1 antibody blocks checkpoint inhibition of T effector cells. Extensive preclinical studies demonstrate that T3011 (and murine equivalent T3855) has potent antitumor activities. Methods: This phase 1 multicenter, open-label, dose escalation study evaluates the safety of intratumoral (IT) T3011 given once every other week (Q2W) in patients (pts) with advanced cutaneous or subcutaneous malignancies. The primary objective is to determine the Recommended Phase 2 Dose of T3011 based on the overall safety, pharmacokinetic and pharmacodynamic profile. Eligible pts are ≥ 18 years, have cutaneous or subcutaneous advanced cancer that has progressed on standard treatment and at least 1 measurable tumor lesion (≥ 10 mm) suitable for T3011 IT injection. Part 1 of the study uses a 3+3 design to evaluate the safety and tolerability of T3011 monotherapy in 4 escalating doses (1 × 106, 1 × 107, 5 × 107, and 1 × 108 PFU/mL). Up to 4 mL of T3011 may be injected based on tumor size. Total enrollment will be determined by toxicities observed. Results: As of Feb. 14, 8 pts have received IT T3011 (Q2W): 3 in Cohort 1 (1 × 106), 3 in Cohort 2 (1 × 107), and 2 in Cohort 3 (5.0 × 107 PFU/ml). Maximum doses per pt was 11. Enrollment continues in Cohort 3. T3011 was well tolerated with no ≥ Grade 3 treatment-related adverse events (AEs), no DLTs or treatment-related SAEs reported to date. Common AEs were pain at injection site, leukopenia, anemia, hypocalcemia, nausea, fever, headache, dermatitis, and diaphoresis. Viral shedding was analyzed in blood, urine and saliva at various times during the study. No Viral DNA was detected in blood or urine samples (first 3 pts analyzed) to date. Biopsy samples taken from injected tumors from 2 melanoma pts (Cohort 1) revealed significant reduction of viable tumor cells after 4 injections (Week 9) compared with baseline. In particular, one post-treatment biopsy contained 45% tumor necrosis area with dramatic increases of CD8 + and NKT cells. CD3+ and CD4+ cells as well as PD-1 expression were increased in post-treatment biopsies of both pts. Conclusions: T3011 IT injection was well tolerated at the first 2 dose levels. Post treatment biopsies from 2 pts (Cohort 1) demonstrated significantly reduced tumor cell viability as well as increased lymphocyte infiltration indicating on-target anti-tumor activities of T3011. To date, 5 out of 6 evaluable pts had SD as best response and 6 enrolled pts remain on study. Dose escalation is continuing. Clinical trial information: NCT04370587.

Is radiation necrosis in radiated melanoma brain metastasis increasing because immunotherapy is contributing to this or are patients just living longer?

e21518

Background: The use of immune checkpoint inhibitors, particularly combination ipilimumab and nivolumab, has drastically changed the management of patients with melanoma brain metastasis. Select patients also benefit from brain-directed stereotactic radiation. Radiation necrosis is a risk associated with stereotactic radiation that oncologists have been observing more frequently in the era of immunotherapy. Methods: Patients were identified who had a history of metastatic melanoma treated with stereotactic brain radiation who subsequently developed radiation necrosis. Brain tissue from those patients with a subsequent resection of their radiation necrosis was obtained and examined for immune infiltrate and other factors. The tissue obtained was evaluated by blinded pathologists who graded % viable tissue, % necrosis, % tumor and % fibrosis. In addition, they graded inflammation on a scale of 1-3. Results: Seven patients were identified who had surgery for radiation necrosis following radiation to melanoma brain metastasis. Tissue was available for five patients. Two patients had received no prior immunotherapy, one patient had received ipilimumab and two patients received combination ipilimumab and nivolumab. The samples obtained consisted of almost entirely viable brain tissue or necrosis. There was minimal inflammation seen in all patients’ samples including those who had not received immunotherapy and those who had. Conclusions: Radiation necrosis in patients on immunotherapy who receive brain-directed stereotactic radiation is a rising problem. On pathologic evaluation increased immune infiltrate is not observed in patients on immunotherapy with radiation necrosis compared to those who never received immunotherapy. This suggests that the increased rates of radiation necrosis may be more likely associated with longer survival as opposed to a direct causative effect from the immunotherapy although with our limited sample size this will need further exploration.[Table: see text]

A phase II study of ERK inhibition by ulixertinib (BVD-523) in metastatic uveal melanoma

10036

Background: Uveal melanoma is a rare and aggressive subset of melanoma that is minimally responsive to traditional therapies. Greater than 80% of uveal melanomas have a mutation in GNAQ or GNA11 which lead to downstream signaling through the MAPK pathway. This has led to efforts to treat uveal melanoma with MEK inhibition with mixed results. Ulixertinib (BVD-523) is a potent and reversible small molecule ATP-competitive inhibitor of both ERK1 and ERK2 protein kinases which has undergone phase I testing. Methods: We performed a phase II study to determine the efficacy and safety of BVD-523 in patients with metastatic uveal melanoma. This was conducted as a Simon two-stage design with a total sample size of 25 patients (pts) and an initial evaluation of efficacy after 13 pts. Two responses were required to continue to the second stage. Results: From April 2018 to April 2019 thirteen pts were enrolled. Pts were predominantly female (69%) with a median age of 64 yrs. (34 -76). Sites of metastasis included liver (84.6%) and lung (30.8%). Grade 3 and 4 toxicities associated with therapy were consistent with BVD-523 and other ERK inhibitors and included LFT elevation, hyponatremia, pruritis, amylase elevation, anemia and rash. The best response, per RECIST 1.1, was stable disease (SD) in 4 pts, and disease progression (PD) in 7 patients. Two patients were unevaluable for response due to withdrawing themselves from the study. Median time to progression was 2.0 months (90% CI: 1.8 – 3.6 mos.). There were eight deaths due to disease progression with a median survival time of 6.9 months (90%CI: 3.2 to 8.3 mos.). Analysis of correlative data from pre- and on-treatment biopsies exploring the change in expression of key signaling proteins relating to treatment is underway. Conclusions: ERK inhibition with ulixertinib (BVD-523) did not demonstrate activity in patients with metastatic uveal melanoma. The toxicities observed on study were consistent with what would be expected with MAPK pathway inhibition. Clinical trial information: NCT03417739.

CTEP 9557: A dose-escalation trial of combination dabrafenib, trametinib, and AT13387 in patients with BRAF mutant solid tumors

3609

Background: Combination BRAF and MEK inhibitor therapy is associated with response in patients (pts) with BRAF mutant (mut) solid tumors; however critical limitations for the durable activity of these agents remains. Preclinically, the addition of heat shock protein 90 (HSP90) inhibitors improves the efficacy of BRAF inhibitor (BRAFi) therapy in both BRAFi -sensitive and resistant mutant cell lines. Methods: CTEP study 9557 (NCT02097225) is a phase I study designed to determine the safety and efficacy of the small molecule HSP90inhibitor, AT13387, in combination with dabrafenib (dab) and trametinib (tram) in patients with BRAF V600E/K mut solid tumors. Prior chemotherapy, immunotherapy, BRAF and/or MEK exposure was permitted. The primary objective was to determine the maximum tolerated dose (MTD). Results: From July 2015 to June 2018, 22 patients with previously treated, metastatic BRAF V600E/K mut solid tumors were enrolled using a 3 + 3 design at four dose levels (DL) (Table). Pts were predominantly female (59%) with a median age of 57.5yrs (37 -75). The most common tumor type was BRAF V600Emut colon cancer (N=12). Dose limiting toxicities (DLTs) occurred in one patient in DL3 and one in DL4, specifically grade 3 myelosuppression and fatigue, respectively. The MTD was Dab 150mg [BID/PO], Tram 2mg [QD/PO] and AT1187 260mg/m2 [D1,8,15/IV]. Twenty-one of 22 pts were eligible for efficacy assessment. Best response, per RECIST 1.1, was partial response (PR) in 2 pts – one with colon ca (TKI-naïve), one with melanoma (TKI-resistant) - stable disease (SD) in 8 pts, and disease progression (PD) in 11 with a disease control rate (PR + SD) of 47.6% (90% CI: 29% - 67%). Median time to progression was significantly longer in DL3 (3.9 mths; 1.8-9.2) compared to DL1 (1.6mths; 0.9-1.7) or DL2 (1.5; 0.6-3.6). Median PFS and OS were 1.8mths (90% CI: 1.6 – 3.7mths) and 5.1 mths (90% CI: 2.5 -10.6mths), respectively. Median OS was not reached in DL3/4. Correlative data on the expression of the key signaling proteins relating to response will be presented at the meeting. Conclusions: HSP90 inhibition combined with BRAF/MEK inhibition was determined to be safe with evidence of disease control in a heavily pre-treated population of pts with BRAF V600E/K mut solid tumors. Clinical trial information: NCT02097225 . [Table: see text]

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.

Association of vitamin D intake with decreased risk of immune checkpoint inhibitor-induced colitis

89

Background: There is a lack of predictive markers informing on the risk of colitis in patients treated with immune checkpoint inhibitors (ICIs). The aim of this study was to identify potential factors associated with development of ICI colitis. Methods: We performed a retrospective analysis of melanoma patients at Dana-Farber Cancer Institute who received PD-1, CTLA-4, or combination blockade between May 2011 to October 2017. Clinical and laboratory characteristics associated with pathologically confirmed ICI colitis were evaluated using multivariate logistic regression analyses. External validation was performed on an independent cohort from Massachusetts General Hospital. Results: The discovery cohort included 213 patients of whom 37 developed ICI colitis (17%). The odds of colitis were higher in patients treated with ipilimumab either as monotherapy or in combination with nivolumab compared to those treated with pembrolizumab. Vitamin D use was recorded in 66/213 patients (31%) before starting ICIs. In multivariable regression analysis, vitamin D use conferred significantly reduced odds of developing ICI colitis (OR 0.35, 95% CI 0.1–0.9). These results were confirmed in the validation cohort of 169 patients of whom 49 developed ICI colitis (29%). Pretreatment neutrophil/lymphocyte ratio (NLR) ≥5 predicted reduced odds of colitis (OR 0.34, 95% CI 0.1–0.9) only in the discovery cohort. Conclusions: This is the first study to report that among patients treated with ICIs, vitamin D intake is associated with reduced risk for ICI colitis. This finding is consistent with prior reports of prophylactic use of vitamin D in ulcerative colitis and GVHD. This observation should be validated prospectively in future studies. [Table: see text]

Characterization of the genetics of mucosal melanoma in patients treated with immunotherapy

9556

Background: Mucosal melanomas can be effectively treated with checkpoint inhibitors, although the response rates are lower than those observed for melanomas arising in cutaneous sites. The mechanistic basis for the lower efficacy of immunotherapies in mucosal melanoma has been suggested to be related to their lower mutational burden. However, there has been limited characterization of the genetics in this melanoma subtype. Methods: Tumor genotyping was performed on all mucosal melanoma patients seen within the Dana Farber Cancer Institute from 2011 until the present by Oncopanel analysis. Results: We identified a total of 57 mucosal melanoma patients whose tumors had been genotyped. Of these 42 received immunotherapy and had response data available. Within the cohort of mucosal melanoma patients, 37.3% had durable clinical benefit (DCB) to their first line of IO therapy. These patients had an average mutational burden/megabase of 6.41 (95% CI 3.53-11.01) but tumor mutational burden did not correlate with response in this cohort. The pattern of mutations in mucosal melanomas was distinct from cutaneous melanomas, as the most frequent mutations were in SF3B1, ATRX, KIT and NF1 genes. Patients with KIT aberrations had a higher DCB rate compared patients with wildtype KIT (73 vs. 33%). In addition, there were several genetic differences observed based upon the site of origin of the mucosal melanoma. A higher rate of SF3B1 mutations was observed in patients with melanoma of anal/rectal origin while patients with vulvar/vaginal melanoma had higher rates of ATRX mutations, which frequently correlated with p53 ( TP53) mutations. Conclusions: This analysis is one of the first to look at genetic patterns in a large cohort of a relatively rare type of melanoma and correlate with response. Our findings confirm the low mutational burden observed in mucosal melanoma despite the high response rate observed in these patients. In addition, this study uncovered a higher rate of response to immunotherapy in mucosal melanoma patients with a KIT mutation.

High prevalence of IBD-associated genetic variants in patients (pts) with immune checkpoint inhibitor (ICI) enteritis/colitis

2582

Background: Colitis is a frequent toxicity of ICI therapy but there is paucity of data on risk factors. Specific serological markers and genetic polymorphisms have been associated with inflammatory bowel disease (IBD) (ulcerative colitis, Crohn’s disease). However, the prevalence of these markers in pts with ICI colitis is unknown. We performed a pilot study to determine the prevalence of IBD-associated genetic and serologic biomarkers in pts with ICI colitis. Methods: Cancer pts with histologically confirmed ICI enteritis/colitis and no history of IBD underwent commercial IBD panel testing. The panel included 4 genetic markers ( ATG16L1, NXK2–3, ECM1, STAT3), 8 serological markers (anti-A4-Fla2, anti-A4-FlaX, anti-CBir1, anti-OmpC, ASCAIgA, ASCA-IgG, pANCA, ANCA), and 5 inflammatory markers (vascular endothelial growth factor [VEGF], intracellular adhesion molecule 1[ICAM-1], vascular cell adhesion molecule 1 [VCAM-1], C-reactive protein, serum amyloid A [SAA]). Clinical testing on serum samples was performed by Prometheus Laboratories (San Diego, CA). Results: Of 15 cancer pts with biopsy confirmed ICI colitis, 10 (67%) were homozygous for 1 or more of 4 genetic markers. The remaining 5 pts were all heterozygous for two or more of the genetic markers. One or more serologic markers associated with IBD were elevated in 7/15 (47%) pts. Serum reactivity was noted for ASCA-IgA (1/15, 7%), ASCA-IgG (1/15, 7%), anti-OmpC (3/15, 20%), anti-CBR IgG (2/15, 13%), anti-A4-FlaX (1/15, 7%), and ANCA (2/15, 13%). One or more inflammatory markers were elevated in 13/15 (88%) pts. Elevations in VEGF, VCAM-1, ICAM-1, and SAA were noted in 2 (13%), 8 (53%), 8 (53%), and 11 (73%) pts, respectively. Only 6 (40%) pts had elevations in CRP levels despite the presence of active inflammation on biopsy. The IBD panel was reported as being consistent with Crohn’s disease in 2 pts, ulcerative colitis in 1 pt and inconclusive for type but consistent with IBD in 1 pt. Conclusions: In this pilot study, all patients with ICI colitis, were either homozygous or heterozygous for two or more high risk IBD alleles. If validated, such testing may prospectively identify pts at risk for developing ICI colitis.

First-in-class oral ERK1/2 inhibitor Ulixertinib (BVD-523) in patients with advanced solid tumors: Final results of a phase I dose escalation and expansion study

2508

Background: Aberrant MAPK pathway activation is known to be an oncogenic driver in many solid tumors, making ERK inhibition an attractive therapeutic strategy. Ulixertinib is an oral ERK1/2 inhibitor that demonstrated potent activity in vitro and tumor regression in BRAF and RAS mutant xenograft models. Methods: This multi-center phase I trial enrolled patients (pts) with advanced solid tumors. Dose escalation utilized an accelerated 3+3 design; expansion cohorts included BRAF or NRAS mutant melanoma and other BRAF or MEK mutant cancers. Study objectives were to characterize dose limiting toxicities (DLTs), maximum tolerated dose (MTD), toxicity profile, pharmacokinetics, pharmacodynamics and preliminary anti-tumor activity by RECIST 1.1. Results: A total of 135 pts were enrolled. Dose escalation enrolled 27 pts (10-900 mg BID) and established the MTD and recommended phase 2 dose (RP2D) of 600 mg BID. DLTs included rash, diarrhea, elevated AST, and elevated creatinine. Drug exposure was dose proportional up to the RP2D, which provided near-complete inhibition of ERK activity in whole blood. In the 108 pt expansion cohort, there were no drug related deaths; however, 32% of pts required a dose reduction. The most common adverse events were rash (49%), diarrhea (47%), fatigue (41%), and nausea (37%). In addition to 3 pts with partial responses during escalation (11%), an additional 9 of 83 (11%) evaluable pts at expansion had a partial response: 1 melanoma pt refractory to prior BRAFi/MEKi treatment, 3 NRAS mutant melanoma pts, 2 pts with BRAF V600E mutant lung cancers including response in brain metastases, 1 with BRAF V600E mutant glioblastoma multiforme, 1 with BRAF G469A head & neck cancer, and 1 with BRAFL485W gallbladder cancer. The duration of response ranged from 2 to 24+ months. Conclusions: Ulixertinib at 600 mg twice a day has an acceptable safety profile and has produced durable responses in pts with NRAS mutant melanoma, BRAF V600 and non-V600 mutant solid tumors including melanoma, glioblastoma multiforme, lung cancers with brain metastases, gallbladder and head & neck cancers. These data support further clinical development of ulixertinib. Clinical trial information: NCT01781429.

Immune-related tumor response dynamics in melanoma patients (pts) treated with pembrolizumab: Identifying markers for clinical outcome and treatment decisions

9521

Background: PD-1 inhibitors have shown marked efficacy in advanced melanoma and are associated with unique response patterns. We aimed to characterize the tumor burden dynamics and identify quantitative imaging markers for overall survival (OS) in melanoma pts treated with pembrolizumab. Methods: The study included 107 advanced melanoma pts (63 males; median age: 63) treated with pembrolizumab monotherapy at DFCI. Tumor burden dynamics were assessed on serial CT scans during therapy by irRECIST, which uses unidimensional measurements and includes new lesions in tumor burden [Clin Cancer Res. 2013;19:3936-43]. The relationships between tumor burden dynamics and OS were studied. Results: Among 107 pts, 96 pts had measurable tumor burden at baseline and 11 had non-target lesions alone at baseline. Among the 96 pts, maximal tumor shrinkage ranged from -100% to 567% (median:-18.5%). Overall response rate was 44% (42/96; irCR in 5, irPR in 37). Tumor burden remained < 20% increase from baseline throughout therapy in 57 pts (55%). Using a 3-month landmark analysis, pts with < 20% tumor burden increase from baseline at 3 months had longer OS than pts with ≥ 20% increase (12-month OS rate: 82 vs. 53%). In extended Cox models, pts with < 20% tumor burden increase during therapy had significantly reduced hazards of death (HR = 0.19, 95%CI: 0.08–0.43, p < 0.0001 univariate; HR = 0.18, 95%CI: 0.08-0.41, p < 0.0001, multivariable). Five pts (5%) experienced pseudoprogression; 3 pts had increase of target lesions with subsequent response, which was noted after confirmed irPD on consecutive scans. Two pts with no measurable tumor burden progressed with new/non-target lesions that subsequently regressed. Conclusions: Tumor burden increase of < 20% from the baseline during pembrolizumab therapy was associated with longer OS, proposing a practical prognostic marker to guide treatment decisions. Pseudoprogressors may experience response after confirmed irPD, indicating a limitation of the current strategy for immune-related response assessment. Evaluations of non-measurable tumor burden may require further attention in the clinical setting of immuno-oncology.