A plain language summary exploring a new treatment combination for untreated locally advanced or metastatic urothelial cancer: enfortumab vedotin plus pembrolizumab

WHAT IS THIS SUMMARY ABOUT?

This summary provides the results of a study of two treatments for cancer, enfortumab vedotin and pembrolizumab, that were studied together against locally advanced or metastatic urothelial cancer (la/mUC), a cancer that occurs most commonly in the bladder.

WHAT WERE THE RESULTS?

In the 45 patients studied, around 16% did have serious side effects, but most side effects were manageable. Twenty-four percent of patients, however, stopped the study treatment because of their side effects. Within about 2 months of starting treatment, most patients' (73%) tumors were smaller and stayed smaller, on average, for more than 2 years.

WHAT DO THE RESULTS MEAN?

The combination of enfortumab vedotin plus pembrolizumab is a new treatment option for patients with locally advanced or metastatic urothelial cancer when they cannot receive the typical treatment, cisplatin. Advanced or metastatic urothelial cancer is a type of cancer where the cancer has already spread outside of the bladder or urinary tract.

Phase I LITESPARK-001 study of belzutifan for advanced solid tumors: Extended 41-month follow-up in the clear cell renal cell carcinoma cohort

BACKGROUND

Accumulation of the HIF-2α transcription factor is an oncogenic event implicated in the tumorigenesis of clear cell renal cell carcinoma (ccRCC). In the phase I LITESPARK-001 study, the first-in-class HIF-2α inhibitor belzutifan demonstrated antitumor activity and an acceptable safety profile for pretreated patients with advanced ccRCC. Updated data with additional follow-up of > 40 months are presented.

METHODS

LITESPARK-001 is an ongoing open-label study with a 3 + 3 dose-escalation design followed by an expansion phase. Patients with ccRCC enrolled at 7 sites received belzutifan 120 mg orally once daily until disease progression, unacceptable toxicity, or patient withdrawal. The data cutoff date was July 15, 2021. The primary end point was identifying the maximum tolerated dose and/or the recommended phase II dose. Secondary end points included objective response rate (ORR) and duration of response (DOR) per RECIST v1.1 by investigator assessment and safety.

RESULTS

Median follow-up was 41.2 months (range, 38.2-47.7). Patients received a median of 3 (range, 1-9) prior systemic therapies. Of 55 patients, 14 (25 %) achieved an objective response. Median DOR was not reached (range, 3.1 + to 38.0 + months). Adverse events (AEs) attributed to study treatment by investigator assessment were reported in 53 patients (96 %). 22 patients (40 %) had grade 3 treatment-related AEs; the most common were anemia (n = 13; 24 %) and hypoxia (n = 7; 13 %). No grade 4 or 5 treatment-related AEs occurred.

CONCLUSION

After a median follow-up of 41.2 months, belzutifan monotherapy demonstrated durable antitumor activity in patients with advanced ccRCC and acceptable safety.

CLINICALTRIALS

gov. NCT02974738.

Correction: AI-Assisted chemical probe discovery for the understudied Calcium-Calmodulin Dependent Kinase, PNCK

[This corrects the article DOI: 10.1371/journal.pcbi.1010263.].

Characterization and Management of Adverse Reactions From the CLEAR Study in Advanced Renal Cell Carcinoma Treated With Lenvatinib Plus Pembrolizumab

BACKGROUND

Lenvatinib plus pembrolizumab showed significantly improved progression-free and overall survival outcomes compared with sunitinib in patients with advanced renal cell carcinoma in the CLEAR study (NCT02811861). Here, we used CLEAR data to characterize common adverse reactions (ARs; adverse-event preferred terms grouped in accordance with regulatory authority review) associated with lenvatinib plus pembrolizumab and review management strategies for select ARs.

MATERIALS AND METHODS

Safety data from the 352 patients who received lenvatinib plus pembrolizumab in the CLEAR study were analyzed. Key ARs were chosen based on frequency of occurrence (≥30%). Time to first onset and management strategies for key ARs were detailed.

RESULTS

The most frequent ARs were fatigue (63.1%), diarrhea (61.9%), musculoskeletal pain (58.0%), hypothyroidism (56.8%), and hypertension (56.3%); grade ≥3 severity ARs that occurred in ≥5% of patients were hypertension (28.7%), diarrhea (9.9%), fatigue (9.4%), weight decreased (8.0%), and proteinuria (7.7%). Median times to first onset of all key ARs were within approximately 5 months (approximately 20 weeks) of starting treatment. Strategies for effectively managing ARs included baseline monitoring, drug-dose modifications, and/or concomitant medications.

CONCLUSION

The safety profile of lenvatinib plus pembrolizumab was consistent with the known profile of each monotherapy; ARs were considered manageable with strategies including monitoring, dose modifications, and supportive medications. Proactive and prompt identification and management of ARs are important for patient safety and to support continued treatment.

CLINICALTRIALS.GOV ID

NCT02811861.

AI-Assisted chemical probe discovery for the understudied Calcium-Calmodulin Dependent Kinase, PNCK

PNCK, or CAMK1b, is an understudied kinase of the calcium-calmodulin dependent kinase family which recently has been identified as a marker of cancer progression and survival in several large-scale multi-omics studies. The biology of PNCK and its relation to oncogenesis has also begun to be elucidated, with data suggesting various roles in DNA damage response, cell cycle control, apoptosis and HIF-1-alpha related pathways. To further explore PNCK as a clinical target, potent small-molecule molecular probes must be developed. Currently, there are no targeted small molecule inhibitors in pre-clinical or clinical studies for the CAMK family. Additionally, there exists no experimentally derived crystal structure for PNCK. We herein report a three-pronged chemical probe discovery campaign which utilized homology modeling, machine learning, virtual screening and molecular dynamics to identify small molecules with low-micromolar potency against PNCK activity from commercially available compound libraries. We report the discovery of a hit-series for the first targeted effort towards discovering PNCK inhibitors that will serve as the starting point for future medicinal chemistry efforts for hit-to-lead optimization of potent chemical probes.

Abstract 722: Epidemiological characterization of renal cell carcinoma in Hispanics: A single US center cohort study

Background: Annually, there are over 400,000 new cases of renal cell carcinoma (RCC) and more than 170,000 deaths worldwide. RCC is one of the top ten more prevalent malignancies in the United States, with 76,000 new cases each year and almost 14,000 deaths. Over the past half-century, RCC has more than doubled in incidence. RCC seems to have a greater incidence among Hispanics with a nearly three-fold increase. The epidemiology of RCC in the Caucasian population has been previously studied. However, there is a knowledge gap on disparities in RCC on minority populations. Studying the epidemiology of RCC in Hispanics is integral to our community where Hispanics make up 70%.

Methods: We conducted a retrospective cohort study to describe the characteristics and rates of recurrence of RCC among patients treated at Sylvester Comprehensive Cancer Center in Miami (which serves four counties in South Florida) between June 2010 to June 2022. We identified ethnicity as Hispanic/Latino (HL) or non-Hispanic/Latino (NHL). Clinical presentation was classified based on the last encounter as local RCC without recurrence, metastatic RCC after nephrectomy, and metastatic RCC at diagnosis/de novo.

Results: We analyzed a total of 2049 patients aged 18 and older diagnosed with RCC, from which 1014 patients (47.90%) were identified as NHL and 933 (48.02%) as HL. A subtotal of 435 patients (22.86%) had metastatic RCC at diagnosis/de novo, from which 245 (55.60%) were NHL, and 176 (40.57%) were HL. A subtotal of 1614 patients (77.14%) were diagnosed with local RCC and underwent nephrectomy, from which 769 (45.61%) were identified as NHL and 787 (50.22%) as HL.

From the NHL group that underwent nephrectomy, 223 patients (28.28%) had recurrent disease, and 546 patients (71.72%) did not. From the HL group, 176 patients (21.81%) had recurrent disease, and 611 (78.19%) did not. Overall, 409 patients had metastasis after nephrectomy, of which 176 (44.5%) were HL, and 203 (52.42%) were NHL.

Conclusions: In this cohort of patients with RCC, almost 50% of patients diagnosed with metastasis were HL. NHL appeared to have more disease recurrence after nephrectomy and higher rates of metastatic disease at diagnosis compared to Hispanics. Further histopathological differences, clinical outcomes, genomic characterization, and rates of clinical trial participation between the NHL and HL cohorts will be presented at the meeting, along with comparisons between US and foreign-born HLs.

Citation Format: Abner A. Murray, Jesus A. Ocejo Gallegos, Sandra Jones, Jose Noy, Rosa L. Frias, Leticia E. Campoverde, Jaime R. Merchan. Epidemiological characterization of renal cell carcinoma in Hispanics: A single US center cohort study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 722.

Lenvatinib plus pembrolizumab versus sunitinib as first-line treatment of patients with advanced renal cell carcinoma (CLEAR): extended follow-up from the phase 3, randomised, open-label study

BACKGROUND

In the primary analysis of the CLEAR study, lenvatinib plus pembrolizumab significantly improved progression-free survival and overall survival versus sunitinib in patients with advanced renal cell carcinoma (data cutoff Aug 28, 2020). We aimed to assess overall survival based on 7 months of additional follow-up.

METHODS

This is a protocol-prespecified updated overall survival analysis (data cutoff March 31, 2021) of the open-label, phase 3, randomised CLEAR trial. Patients with clear-cell advanced renal cell carcinoma who had not received any systemic anticancer therapy for renal cell carcinoma, including anti-vascular endothelial growth factor therapy, or any systemic investigational anticancer drug, were eligible for inclusion from 200 sites (hospitals and cancer centres) across 20 countries. Patients were randomly assigned (1:1:1) to receive lenvatinib (20 mg per day orally in 21-day cycles) plus pembrolizumab (200 mg intravenously every 21 days; lenvatinib plus pembrolizumab group), lenvatinib (18 mg per day orally) plus everolimus (5 mg per day orally; lenvatinib plus everolimus group [not reported in this updated analysis]) in 21-day cycles, or sunitinib (50 mg per day orally, 4 weeks on and 2 weeks off; sunitinib group). Eligible patients were at least 18 years old with a Karnofsky performance status of 70 or higher. A computer-generated randomisation scheme was used, and stratification factors were geographical region and Memorial Sloan Kettering Cancer Center prognostic groups. The primary endpoint was progression-free survival assessed by independent imaging review according to Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST v1.1). In this Article, extended follow-up analyses for progression-free survival and protocol-specified updated overall survival data are reported for the intention-to-treat population. No safety analyses were done at this follow-up. This study is closed to new participants and is registered with ClinicalTrials.gov, NCT02811861.

FINDINGS

Between Oct 13, 2016, and July 24, 2019, 1417 patients were screened for inclusion in the CLEAR trial, of whom 1069 (75%; 273 [26%] female, 796 [74%] male; median age 62 years [IQR 55-69]) were randomly assigned: 355 (33%) patients (255 [72%] male and 100 [28%] female) to the lenvatinib plus pembrolizumab group, 357 (33%) patients (275 [77%] male and 82 [23%] female) to the sunitinib group, and 357 (33%) patients to the lenvatinib plus everolimus group (not reported in this updated analysis). Median follow-up for progression-free survival was 27·8 months (IQR 20·3-33·8) in the lenvatinib plus pembrolizumab group and 19·4 months (5·5-32·5) in the sunitinib group. Median progression-free survival was 23·3 months (95% CI 20·8-27·7) in the lenvatinib plus pembrolizumab group and 9·2 months (6·0-11·0) in the sunitinib group (stratified hazard ratio [HR] 0·42 [95% CI 0·34-0·52]). Median overall survival follow-up was 33·7 months (IQR 27·4-36·9) in the lenvatinib plus pembrolizumab group and 33·4 months (26·7-36·8) in the sunitinib group. Overall survival was improved with lenvatinib plus pembrolizumab (median not reached [95% CI 41·5-not estimable]) versus sunitinib (median not reached [38·4-not estimable]; HR 0·72 [95% CI 0·55-0·93]).

INTERPRETATION

Efficacy benefits of lenvatinib plus pembrolizumab over sunitinib were durable and clinically meaningful with extended follow-up. These results support the use of lenvatinib plus pembrolizumab as a first-line therapy for patients with advanced renal cell carcinoma.

FUNDING

Eisai and Merck Sharp & Dohme.

Fatty acid metabolism reprogramming in ccRCC: mechanisms and potential targets

Lipid droplet formation is a defining histological feature in clear-cell renal cell carcinoma (ccRCC) but the underlying mechanisms and importance of this biological behaviour have remained enigmatic. De novo fatty acid (FA) synthesis, uptake and suppression of FA oxidation have all been shown to contribute to lipid storage, which is a necessary tumour adaptation rather than a bystander effect. Clinical studies and mechanistic investigations into the roles of different enzymes in FA metabolism pathways have revealed new metabolic vulnerabilities that hold promise for clinical effect. Several metabolic alterations are associated with worse clinical outcomes in patients with ccRCC, as lipogenic genes drive tumorigenesis. Enzymes involved in the intrinsic FA metabolism pathway include FA synthase, acetyl-CoA carboxylase, ATP citrate lyase, stearoyl-CoA desaturase 1, cluster of differentiation 36, carnitine palmitoyltransferase 1A and the perilipin family, and each might be potential therapeutic targets in ccRCC owing to the link between lipid deposition and ccRCC risk. Adipokines and lipid species are potential biomarkers for diagnosis and treatment monitoring in patients with ccRCC. FA metabolism could potentially be targeted for therapeutic intervention in ccRCC as small-molecule inhibitors targeting the pathway have shown promising results in preclinical models.

Phase 1, open-label, dose-escalation study on the safety, pharmacokinetics, and preliminary efficacy of intravenous Coxsackievirus A21 (V937), with or without pembrolizumab, in patients with advanced solid tumors

BACKGROUND

Oncolytic virus V937 showed activity and safety with intratumoral administration. This phase 1 study evaluated intravenous V937±pembrolizumab in patients with advanced solid tumors.

METHODS

Patients had advanced non-small cell lung cancer (NSCLC), urothelial cancer, metastatic castration-resistant prostate cancer, or melanoma in part A (V937 monotherapy), and metastatic NSCLC or urothelial cancer in part B (V937+pembrolizumab). Prior immunotherapy was permitted >28 days before study treatment. Patients received intravenous V937 on days 1, 3, and 5 (also on day 8 in part B) of the first 21-day cycle and on day 1 of subsequent cycles for eight cycles. Three ascending dose-escalation cohorts were studied. Dose-escalation proceeded if no dose-limiting toxicities (DLTs) occurred in cycle 1 of the previous cohort. In part B, patients also received pembrolizumab 200 mg every 3 weeks from day 8 for 2 years; dose-expansion occurred at the highest-dose cohort. Serial biopsies were performed.

RESULTS

No DLTs occurred in parts A (n=18) or B (n=85). Grade 3-5 treatment-related adverse events (AEs) were not observed in part A and were experienced by 10 (12%) patients in part B. The most frequent treatment-related AEs (any grade) in part B were fatigue (36%), pruritus (18%), myalgia (14%), diarrhea (13%), pyrexia (13%), influenza-like illness (12%), and nausea (12%). At the highest tested dose, median intratumoral V937 concentrations were 117,631 copies/mL on day 8, cycle 1 in part A (n=6) and below the detection limit for most patients (86% (19/22)) on day 15, cycle 1 in part B. Objective response rates were 6% (part A), 9% in the NSCLC dose-expansion cohort (n=43), and 20% in the urothelial cancer dose-expansion cohort (n=35).

CONCLUSIONS

Intravenous V937+pembrolizumab had a manageable safety profile. Although V937 was detected in tumor tissue, in NSCLC and urothelial cancer, efficacy was not greater than that observed in previous studies with pembrolizumab monotherapy.

TRIAL REGISTRATION NUMBER

NCT02043665.

Enfortumab Vedotin Plus Pembrolizumab in Previously Untreated Advanced Urothelial Cancer

PURPOSE

Cisplatin-based combination chemotherapy remains the standard of care for locally advanced or metastatic urothelial cancer (la/mUC); however, toxicity is substantial, responses are rarely durable, and many patients with la/mUC are ineligible. Each enfortumab vedotin and pembrolizumab have shown a survival benefit versus chemotherapy in UC, are not restricted by cisplatin eligibility, and warrant investigation as a first-line (1L) combination therapy in patients ineligible for cisplatin.

METHODS

In this ongoing phase Ib/II, multicenter, open-label study, 1L cisplatin-ineligible patients with la/mUC received enfortumab vedotin 1.25 mg/kg once daily on days 1 and 8 and pembrolizumab 200 mg (day 1) intravenously once daily in 3-week cycles. The primary end point was safety. Key secondary end points included confirmed objective response rate, duration of response (DOR), and overall survival (OS).

RESULTS

Forty-five patients received enfortumab vedotin plus pembrolizumab. The most common treatment-related adverse events (TRAEs) were peripheral sensory neuropathy (55.6%), fatigue (51.1%), and alopecia (48.9%). Twenty-nine patients (64.4%) had grade 3 or higher TRAEs; the most common were increased lipase (17.8%), maculopapular rash (11.1%), and fatigue (11.1%). One death (2.2%) was classified as a TRAE. The confirmed objective response rate after a median of nine cycles was 73.3% with a complete response rate of 15.6%. The median DOR and median OS were 25.6 months and 26.1 months, respectively.

CONCLUSION

Enfortumab vedotin plus pembrolizumab showed a manageable safety profile. Most patients experienced tumor shrinkage. The median DOR and median OS exceeding 2 years in a cisplatin-ineligible patient population make this a promising combination currently under investigation in a phase III study (ClinicalTrials.gov identifier: NCT04223856).

Anti-CD73 antibody activates human B cells, enhances humoral responses and induces redistribution of B cells in patients with cancer

BACKGROUND

CD73 is widely expressed on immune cells playing a critical role in immunomodulatory functions including cell adhesion and migration, as a costimulatory molecule for T cells and in production of adenosine. The function of CD73 expressed on B cells has not been fully characterized. Mupadolimab is an anti-human CD73 antibody that activates B cells. We evaluated the characteristics of this antibody and its effects on immune cells in vitro and in vivo.

METHODS

Mupadolimab binding to CD73, inhibition of CD73 enzymatic activity, and effects on lymphocyte activation were evaluated in vitro by measuring changes in immunophenotype by flow cytometry. Cryogenic-transmission electron microscopy was used to determine epitope binding. Effects on human B cells in vivo were evaluated in immunodeficient NSG-SGM3 mice immunized with SARS-CoV-2 and influenza viral antigens. Safety and immune effects were evaluated in the completed dose escalation portion of a phase 1 trial conducted in patients with cancer.

RESULTS

Mupadolimab binds to a unique epitope on CD73^POS B cells resulting in their activation and differentiation through B cell receptor signaling pathways. Mupadolimab induces expression of CD69, CD83, CD86 and MHC class II on B cells along with morphological transformation into plasmablasts and expression of CD27, CD38 and CD138. These effects are independent of adenosine. Mupadolimab binds to the N-terminal of CD73 in the closed position and competitively inhibits substrate binding. Mupadolimab enhanced antigen specific antibody response to SARS-CoV-2 spike protein and influenza hemagglutinin in humanized mouse models. Mupadolimab was evaluated as a monotherapy in a phase 1 trial (NCT03454451) in 34 patients with advanced cancer and demonstrated binding to CD73^POS circulating cells and transient reduction in the number of B cells, with return of CD73^NEG B cells with memory phenotype. No dose-limiting toxicities or changes in serum immunoglobulins were seen.

CONCLUSIONS

Mupadolimab activates B cells and stimulates the production of antigen specific antibodies. The effects in patients with cancer suggest that activated, CD69^POS B cells redistribute to lymphoid tissues. Minor tumor regression was observed in several patients. These results support further investigation of mupadolimab as an immunotherapy for cancer and its potential use as a vaccine adjuvant.

TRIAL REGISTRATION NUMBER

NCT03454451.

Phase 1 LITESPARK-001 (MK-6482-001) study of belzutifan in advanced solid tumors: Update of the clear cell renal cell carcinoma (ccRCC) cohort with more than 3 years of total follow-up

4509

Background: Hypoxia-inducible factor 2α (HIF-2α) is a key oncogenic driver in RCC. Antitumor activity of the HIF-2α inhibitor belzutifan has been observed in RCC and is approved for treatment in patients (pts) with VHL disease who require therapy for associated RCC, CNS hemangioblastomas, or pNETs not requiring immediate surgery. Previous data from the phase 1 LITESPARK-001 trial (NCT02974738) designed to evaluate belzutifan in heavily pretreated RCC showed durable antitumor activity and an acceptable safety profile. After more than 3 years of follow-up for pts with ccRCC still receiving treatment, updated data are presented. Methods: Pts enrolled in the ccRCC cohort were previously treated with ≥1 therapy, had RECIST-measurable disease, ECOG PS score of 0 or 1, adequate organ function, and life expectancy of ≥6 months. Pts received oral belzutifan 120 mg once daily. The primary end point was safety. Secondary end points were ORR, DCR (CR + PR + SD), PFS, and DOR per RECIST v1.1 by investigator. The data cutoff date was July 15, 2021. Results: Of 55 pts enrolled in the ccRCC cohort, 9 (16%) remain on treatment as of the data cutoff date of July 15, 2021; the primary reason for discontinuation was progressive disease (n = 34; 62%). Pts received a median of 3 prior therapies (range, 1-9); 39 (71%) received prior VEGF and immunotherapy. Pts were followed while on treatment and for 30 days after the last dose for a median of 41.2 months (range, 38.2-47.7). Twenty-two pts (40%) experienced grade 3 TRAEs. The most common (≥10%) grade 3 TRAEs were anemia (n = 13; 24%) and hypoxia (n = 7; 13%). There were no grade 4 or 5 TRAEs. ORR was 25%, with 1 confirmed CR (2%) and 13 PRs (24%); DCR was 80%. Median DOR was not reached (range, 3.1+ to 37.9+ months); 8 of 14 responding pts (57%) remain in response as of the data cutoff date. Per IMDC risk, 4 of 13 pts with favorable risk achieved response (ORR = 31%; all PRs) and 10 of 42 pts with intermediate/poor risk achieved response (ORR = 24%; 1 CR, 9 PRs). DCR was 92% for pts with favorable risk and 76% for pts with intermediate/poor risk. For pts who received prior VEGF and immunotherapy, 8 of 39 pts achieved response (ORR = 21%; 1 CR; 7 PR); DCR was 74%. For the 16 pts who did not receive prior VEGF/immunotherapy, 6 achieved response (ORR = 38%; all PRs); DCR was 94%. Median PFS for the total cohort was 14.5 months (95% CI, 7.3-22.1); PFS rate at 156 weeks (̃36 months) was 34%. Conclusions: As seen after a median follow-up of > 3 years for pts still receiving treatment, belzutifan monotherapy continued to show a high rate of disease control and durable responses in previously treated pts with advanced ccRCC. Belzutifan exhibited a favorable safety profile, and no new safety signals were observed. In several phase 3 studies, belzutifan is being evaluated as monotherapy and combined therapy for ccRCC. Clinical trial information: NCT02974738.

Impact of subsequent therapies in patients (pts) with advanced renal cell carcinoma (aRCC) receiving lenvatinib plus pembrolizumab (LEN + PEMBRO) or sunitinib (SUN) in the CLEAR study

4514

Background: In the open-label, randomized, phase 3 CLEAR study, LEN + PEMBRO had significant PFS (primary endpoint) and OS (key secondary endpoint) benefits over SUN among pts with aRCC in the 1L setting (Motzer 2021, NEJM). We evaluated PFS on next-line therapy (“PFS2”) and explored the effect of subsequent anticancer therapy on OS in the LEN + PEMBRO and SUN treatment arms of CLEAR. Methods: PFS2 was defined as time from randomization to disease progression (as assessed by investigator) on next-line treatment or death from any cause (whichever occurred first). PFS2 was evaluated in all pts randomly assigned to LEN 20 mg orally QD + PEMBRO 200 mg IV Q3W (n=355) or SUN 50 mg orally QD (4 wks on/2 wks off) (n=357) using Kaplan-Meier estimates, and compared between treatment arms via a log-rank test stratified by geographic region and MSKCC prognostic groups. The HR and corresponding CI were estimated using the Cox regression model with Efron’s method for ties, using the same stratification factors. A post hoc analysis accounting for the effect of subsequent anticancer therapy on OS (time from randomization to death from any cause) in the LEN + PEMBRO and SUN arms using 2-stage estimation was conducted. Results: Among pts who received subsequent anticancer therapy in the LEN + PEMBRO (n=117 pts) and SUN (n=206 pts) arms (Table), median time to next-line therapy was 12.2 mos (range 1.45–37.36) and 6.4 mos (range 0.39–28.52), respectively. Median duration of first subsequent anticancer therapy was 5.2 mos (range 0.10–30.23) in the LEN + PEMBRO arm and 6.8 mos (range 0.03–30.72) in the SUN arm. Among all pts, PFS2 was longer with LEN + PEMBRO than with SUN (median not reached vs 28.7 mos; HR, 0.50; 95% CI 0.39–0.65; nominal P<0.0001); PFS2 rates at 24 and 36 mos are in the Table. The unadjusted OS HR for LEN + PEMBRO vs SUN (from the primary analysis [Motzer 2021, NEJM]) was 0.66 (95% CI 0.49–0.88); the HR for OS adjusted for subsequent therapy was 0.54 (bootstrap 95% CI 0.39–0.72). Conclusions: LEN + PEMBRO had a statistically significant and clinically meaningful benefit over SUN in the CLEAR study. These findings remained consistent after accounting for subsequent therapies, as evidenced by prolonged PFS2 and adjusted OS. Results further support LEN + PEMBRO as a standard of care in 1L aRCC. Clinical trial information: NCT02811861. [Table: see text]

Post hoc analysis of the CLEAR study in advanced renal cell carcinoma (RCC): Effect of subsequent therapy on survival outcomes in the lenvatinib (LEN) + everolimus (EVE) versus sunitinib (SUN) treatment arms

4562

Background: The multicenter, open-label, randomized, phase 3 CLEAR study showed that LEN + EVE had a significant PFS benefit (HR 0.65, 95% CI 0.53-0.80, P<0.001) and improved objective response rate (relative risk 1.48, 95% CI 1.26-1.74) vs SUN in the first-line treatment of patients (pts) with advanced RCC. The difference in overall survival (OS) for LEN + EVE vs SUN was not statistically significant (HR 1.15, 95% CI 0.88-1.50) (Motzer R et al. NEJM. 2021). Post hoc subgroup analyses were performed to assess the impact of subsequent therapy on OS. Methods: Pts in the CLEAR study were randomly assigned (1:1:1) to 1 of 3 treatment arms, including LEN 18 mg + EVE 5 mg once daily (QD) and SUN 50 mg QD (4 weeks on then 2 weeks off). These post hoc analyses examined OS by subsequent systemic anticancer medication in the LEN + EVE and SUN arms. Hazard ratios (HR; LEN + EVE vs SUN) were based on stratified (geographic region and MSKCC prognostic risk groups) Cox proportional hazards model. Results: Among 1069 pts with advanced RCC randomized in the CLEAR study, 714 pts were randomly assigned to the LEN + EVE and SUN arms (N=357/each). The median duration of survival follow-up was 27 months in the LEN + EVE arm and 26 months in the SUN arm. Given the shorter median duration of study treatment with SUN (7.8 months) vs LEN + EVE (11.0 months), more pts in the SUN arm received subsequent anticancer therapy during survival follow-up (LEN + EVE, n=167; SUN, n=206). Among pts who received subsequent therapy, pts in the LEN + EVE arm had a longer median time from randomization to initiation of subsequent therapy vs those in the SUN arm (8.0 vs 6.6 months, respectively). OS for the overall population, for pts with no subsequent anticancer therapy, and for pts with no subsequent immunotherapy is shown in the table. In the US population subgroup (LEN + EVE, n=62; SUN, n=61) of the CLEAR study, in which a similar number of pts received subsequent systemic anticancer therapies in the LEN + EVE vs SUN arms (62.9% vs 65.6%, respectively), OS was comparable among the 2 arms (HR 0.95, 95% CI 0.51-1.76). Overall, the safety profile was consistent with the known safety profiles of LEN + EVE and SUN. In both arms, most treatment-emergent deaths were due to progressive disease; there were few treatment-related deaths (<1%, per arm) and no clustering of events. Conclusions: In the CLEAR study, LEN + EVE met the primary endpoint of a significant benefit in PFS vs SUN. The results of these exploratory analyses suggest that subsequent systemic anticancer therapy affected the OS outcome results for LEN + EVE vs SUN in the CLEAR study. Clinical trial information: NCT02811861. [Table: see text]

Association of ATM mutations in metastatic prostate cancer with differential genomic alteration profiles from homologous recombination deficient and proficient tumors

5063

Background: ATM mutations, one of a family of DNA repair defects prevalent in prostate cancer, have been included in a list of actionable mutations for PARP inhibitor (PARPi) therapeutic trials. Despite preclinical evidence, PARPi have shown minimal clinical activity in ATM mutant prostate cancer (ATMmPCa). The present analysis explores co-occurring genomic alterations that may drive outcomes of metastatic PCa (mPCa) patients with tumors harboring ATM mutations and provide clues for understanding therapy resistance and potential targets. Methods: This study included molecular profiling analysis of 1375 cases of mPCa. Tumors were analyzed using next-generation sequencing (NGS), whole transcriptome sequencing (WTS), and immunohistochemistry (IHC) (Caris Life Sciences, Phoenix, AZ). dMMR/MSI-H status was determined by IHC, NGS, and fragment analysis and tumor mutational burden (TMB) was calculated based on somatic nonsynonymous missense mutations. We performed differential gene expression analysis of HR-associated transcripts such as ATR, PARP1-3, RAD50, RAD51A/B/C/D and RAD54. Significance was determined using the ꭓ2 test and Benjamini-Hochberg method. Results: Fifty-nine (4.2%) cases harbored pathogenic ATM mutations, 84 (6.2%) harbored BRCA2 mutations. 1018 tumors (74%) were deemed homologous recombination proficient (HRP) and 155 tumors (11.3%) were HR Deficient (HRD); harboring one or more mutation in HR-related genes excluding ATM and BRCA2. The mutation rate of TP53 was significantly lower in ATMmPCa (12.0%) compared to BRCA2mPCa (35%), HRD (35%) and HRP (46.6%) tumors. ATMmPCa showed higher rates of SMAD2 (3.7%/1%) and FLCN (5.2%/0.3%) alterations compared to HRP cases. PARP1 and RAD51D gene expression was reduced in ATMmPCa compared to HRP (p < 0.05) and BRCA2mPCa ( p < 0.05) tumors, respectively. No differences in gene expression levels were detected for ATR, PARP2, PARP3, RAD50, and RAD54. Chromosomal segments demonstrating differential CNA in ATMmPCa vs HRP, HRD, or BRCA2mPCa included FGF19, FGF4, PTPN11, ALDH2, DAXX, BCL7A, CCND1, BMPR1A and MEF2B (Q-value < 0.05 determined by ꭓ2). The most common CNA in ATMmPCa was CCND1, present in approximately 13% (7/55) of cases. Compared to BRCA2mPCa and HRD cases, ATMmPCa cases are less likely to display markers of immunotherapy response such as dMMR/MSI-H or TMB ≥10 mutations/MB. Conclusions: ATMmPCa demonstrated several differences in co-occurring alterations compared to BRCA2mPCa, HRD and HRP mPCa. ATMmPCa tumors were less likely to harbor alterations in TP53 compared to BRCA2, HRD or HRP tumors. CNA in ATMmPCa occurred in 9 genes across distinct mPCa molecular subtypes and were enriched for those associated with the 11q13 amplicon harboring Cyclin D1. The FGF and PTPN11 related pathways are potentially targetable pathways in ATMmPC and may merit further study.

Inhibition of hypoxia-inducible factor-2α in renal cell carcinoma with belzutifan: a phase 1 trial and biomarker analysis

Hypoxia-inducible factor-2α (HIF-2α) is a transcription factor that frequently accumulates in clear cell renal cell carcinoma (ccRCC), resulting in constitutive activation of genes involved in carcinogenesis. Belzutifan (MK-6482, previously known as PT2977) is a potent, selective small molecule inhibitor of HIF-2α. Maximum tolerated dose, safety, pharmacokinetics, pharmacodynamics and anti-tumor activity of belzutifan were evaluated in this first-in-human phase 1 study (NCT02974738). Patients had advanced solid tumors (dose-escalation cohort) or previously treated advanced ccRCC (dose-expansion cohort). Belzutifan was administered orally using a 3 + 3 dose-escalation design, followed by expansion at the recommended phase 2 dose (RP2D) in patients with ccRCC. In the dose-escalation cohort (n = 43), no dose-limiting toxicities occurred at doses up to 160 mg once daily, and the maximum tolerated dose was not reached; the RP2D was 120 mg once daily. Plasma erythropoietin reductions were observed at all doses; erythropoietin concentrations correlated with plasma concentrations of belzutifan. In patients with ccRCC who received 120 mg once daily (n = 55), the confirmed objective response rate was 25% (all partial responses), and the median progression-free survival was 14.5 months. The most common grade ≥3 adverse events were anemia (27%) and hypoxia (16%). Belzutifan was well tolerated and demonstrated preliminary anti-tumor activity in heavily pre-treated patients, suggesting that HIF-2α inhibition might offer an effective treatment for ccRCC.

Lenvatinib plus Pembrolizumab or Everolimus for Advanced Renal Cell Carcinoma

BACKGROUND

Lenvatinib in combination with pembrolizumab or everolimus has activity against advanced renal cell carcinoma. The efficacy of these regimens as compared with that of sunitinib is unclear.

METHODS

In this phase 3 trial, we randomly assigned (in a 1:1:1 ratio) patients with advanced renal cell carcinoma and no previous systemic therapy to receive lenvatinib (20 mg orally once daily) plus pembrolizumab (200 mg intravenously once every 3 weeks), lenvatinib (18 mg orally once daily) plus everolimus (5 mg orally once daily), or sunitinib (50 mg orally once daily, alternating 4 weeks receiving treatment and 2 weeks without treatment). The primary end point was progression-free survival, as assessed by an independent review committee in accordance with Response Evaluation Criteria in Solid Tumors, version 1.1. Overall survival and safety were also evaluated.

RESULTS

A total of 1069 patients were randomly assigned to receive lenvatinib plus pembrolizumab (355 patients), lenvatinib plus everolimus (357), or sunitinib (357). Progression-free survival was longer with lenvatinib plus pembrolizumab than with sunitinib (median, 23.9 vs. 9.2 months; hazard ratio for disease progression or death, 0.39; 95% confidence interval [CI], 0.32 to 0.49; P<0.001) and was longer with lenvatinib plus everolimus than with sunitinib (median, 14.7 vs. 9.2 months; hazard ratio, 0.65; 95% CI, 0.53 to 0.80; P<0.001). Overall survival was longer with lenvatinib plus pembrolizumab than with sunitinib (hazard ratio for death, 0.66; 95% CI, 0.49 to 0.88; P = 0.005) but was not longer with lenvatinib plus everolimus than with sunitinib (hazard ratio, 1.15; 95% CI, 0.88 to 1.50; P = 0.30). Grade 3 or higher adverse events emerged or worsened during treatment in 82.4% of the patients who received lenvatinib plus pembrolizumab, 83.1% of those who received lenvatinib plus everolimus, and 71.8% of those who received sunitinib. Grade 3 or higher adverse events occurring in at least 10% of the patients in any group included hypertension, diarrhea, and elevated lipase levels.

CONCLUSIONS

Lenvatinib plus pembrolizumab was associated with significantly longer progression-free survival and overall survival than sunitinib. (Funded by Eisai and Merck Sharp and Dohme; CLEAR ClinicalTrials.gov number, NCT02811861.).

Phase 3 trial of lenvatinib (LEN) plus pembrolizumab (PEMBRO) or everolimus (EVE) versus sunitinib (SUN) monotherapy as a first-line treatment for patients (pts) with advanced renal cell carcinoma (RCC) (CLEAR study)

269

Background: In pts with advanced RCC, second-line treatment with LEN + EVE prolonged progression-free survival (PFS) compared with EVE alone. LEN + PEMBRO, also showed preliminary efficacious evidence in a phase 1/2 RCC study. Here, we describe the investigational study results of first-line LEN + PEMBRO or LEN + EVE versus SUN in pts with advanced RCC. Methods: Pts were randomized (1:1:1) to receive LEN 20 mg orally once daily + PEMBRO 200 mg IV every 3 weeks (wks); or LEN 18 mg + EVE 5 mg orally once daily; or SUN 50 mg orally once daily (4 wks on/2 wks off). Eligible pts had advanced RCC with no prior systemic therapy. Randomization was stratified by geographic region and MSKCC prognostic group. The primary endpoint was PFS by Independent Review Committee per RECIST v1.1. Secondary endpoints included overall survival (OS), objective response rate (ORR) and safety. A sequential approach was used to test PFS first, then OS and ORR. PFS and OS were compared across arms by a stratified log-rank test; hazard ratios (HRs) were estimated by a stratified Cox regression model. Results: 1069 pts were randomized (Table). After a median follow-up of 27 months (data cutoff August 28, 2020), PFS was significantly improved with LEN + PEMBRO (median 24 months [mos]) vs SUN (median 9 mos; HR 0.39, 95% CI 0.32–0.49) and LEN + EVE (median 15 mos) vs SUN (HR 0.65, 95% CI 0.53–0.80). OS was significantly longer with LEN + PEMBRO vs SUN (HR 0.66, 95% CI 0.49–0.88), whereas OS with LEN + EVE vs SUN was not statistically different (HR 1.15, 95% CI 0.88–1.50). ORR was significantly greater with LEN + PEMBRO (ORR 71%; complete response [CR] 16%) vs SUN (ORR 36%; CR 4%; odds ratio 4.35, 95% CI 3.16–5.97) and LEN + EVE (ORR 54%; CR 10%) vs SUN (odds ratio 2.15, 95% CI 1.57–2.93). Grade ≥3 treatment-related adverse events occurred in 72% of pts in the LEN + PEMBRO arm and 73% of pts in the LEN + EVE arm compared with 59% of pts in the SUN arm. Conclusions: LEN + PEMBRO demonstrated significant improvements in PFS, OS and ORR vs SUN. LEN + EVE demonstrated significant improvements in PFS and ORR vs SUN. Safety was manageable and consistent with the known single-agent profiles. Clinical trial information: NCT02811861 . [Table: see text]

Impact of FGFR2/3 activating genomic alterations on response to enfortumab vedotin in metastatic urothelial carcinoma (mUC)

472

Background: Enfortumab Vedotin (EV), an antibody-drug conjugate that targets nectin-4, is approved for metastatic urothelial carcinoma (mUC) progressing post-platinum and PD1/L1 inhibitor therapy. Erdafitinib is approved in patients for post-platinum mUC with activating genomic alterations in FGFR2/3, but the activity of EV in this subset is unclear. We investigated the activity of EV in patients (pts) with mUC based on FGFR2/3 genotype to inform management. Methods: In this multi-center, retrospective analysis, we assessed the objective response rate (ORR) to EV in mUC pts with and without FGFR2/3 genomic alterations detected by targeted panel next-generation sequencing. Activating gene fusions and known hotspots mutations in the two genes were considered. Descriptive analysis of ORR and patient characteristics was performed. Fisher’s exact test and binomial test with two-tailed p-value were used. Results: 40 pts were available from 4 institutions. Most pts were male (31/40, 78%) and the median age at start of EV was 74.1 (range 49 – 90) years. Ten patients (25%) had upper tract urothelial carcinoma (UTUC), and 33 (82%) had baseline ECOG performance status of 0-1. 31 of 39 patients had received both platinum-based chemotherapy and PD1/L1 inhibitors. Seven patients had confirmed activating hotspot FGFR3 mutations (p.S249C or p.Y373C). One pt had FGFR2 high-level amplification (HA), and one had FGFR3 HA. Of 36 patients evaluable for ORR, 18 had partial response (PR), 12 had stable disease (SD) and 6 had progressive disease (PD). Patients with FGFR2/3 activating mutations exhibited an ORR that was not statistically different compared to patients without no mutations: 2/7 (29%; 90% CI: 5 – 66%) vs. 16/29 (55%; 90% CI: 38 – 71%) respectively ( p-value = 0.4). 3/7 patients with FGFR3 hotspot mutations received an FGFR2/3 inhibitor and none responded; one of them had a sequential response to EV. Conclusions: In this multi-center retrospective cohort, FGFR2/3 activating genomic alterations did not appear to compromise response to EV in mUC. Larger studies are required to confirm our findings and optimal sequencing of EV and erdafitinib in mUC pts with FGFR2/3 genomic alterations requires further assessment.

The oral HIF-2 α inhibitor MK-6482 in patients with advanced clear cell renal cell carcinoma (RCC): Updated follow-up of a phase I/II study

273

Background: Clear cell RCC (ccRCC) accounts for ~70% of kidney cancer cases in the US. Several first-line therapies are approved for ccRCC, but few patients respond completely and most progress within 5-11 mo. A key oncogenic driver in RCC is the transcription factor hypoxia-inducible factor 2α (HIF-2α). MK-6482 is a small molecule HIF-2α inhibitor that blocks the heterodimerization of HIF-2α with HIF-1β, inducing tumor regression in mouse xenograft RCC models. Updated data presented here include additional follow-up from the expansion cohort of patients with ccRCC from the first-in-human phase 1/2 study of MK-6482 in advanced solid tumors (NCT02974738). Methods: Patients were aged ≥18 y with advanced ccRCC, received ≥1 prior therapy, and had RECIST v1.1 measurable disease, ECOG status 0 or 1, adequate organ function, and life expectancy ≥6 mo. They received 120 mg of MK-6482 orally once daily. Tumors were assessed at baseline, within 7 days before week 9, and then every 8 weeks; response was assessed using RECIST v1.1. The primary end point was safety. Secondary end points included ORR, duration of response (DOR), and PFS. Results: Fifty-five patients with ccRCC were treated with MK-6482 120 mg (52 in expansion and 3 in dose-escalation cohorts). The median number of prior therapies was 3 (range 1-9). Forty-two patients (81%) previously received PD-1/L1 inhibitors and 48 (92%) previously received VEGF inhibitors. Thirteen patients (24%) were classified as favorable risk and 42 (76%) as intermediate or poor risk per IMDC criteria. With a median follow-up of 28 mo, the most common all-grade, all-cause AEs >30% were anemia (76%), fatigue (71%), dyspnea (49%), nausea (36%), cough (31%), and hypoxia (31%). Anemia (27%) and hypoxia (16%) were the most common grade 3 AEs. Two patients (4%) experienced grade 4 AEs, and 4 patients (7%) experienced grade 5 AEs. No grade 4 or 5 AEs were related to treatment. ORR was 25%, with 14 confirmed PRs. Thirty patients (55%) had SD, with a disease control rate (CR+PR+SD) of 80%. Median DOR was not reached; 77% had a response ≥6 mo. By IMDC risk, 4 of 13 patients with favorable risk had PR (ORR = 31%) and 10 of 42 with intermediate or poor risk had PR (ORR = 24%); disease control rate was 92% and 76%, respectively. Median PFS for the total population was 14.5 mo; 51% had a PFS of 12 mo. As of June 1, 2020, 33 patients (60%) discontinued because of PD and 2 (4%) because of AEs; 11 patients (20%) had ongoing treatment. Conclusions: MK-6482 remained well tolerated with a favorable safety profile and promising single-agent activity in patients with ccRCC for all IMDC risk groups after further follow-up. A phase III trial in a similar population is underway. Clinical trial information: NCT02974738 .

Relationship of infusion duration to safety, efficacy, and pharmacodynamics (PD): Second part of a phase I-II study using VSV-IFNβ-NIS (VV1) oncolytic virus in patients with refractory solid tumors

3090

Background: VV1 (Voyager V1) is derived from VSV, an RNA virus with low human seroprevalence, engineered to replicate selectively in and kill human cancer cells. In Part 1 of this study, we demonstrated the safety of intratumoral VV1 and dose-response, using serum IFNβ as a biomarker; we observed viral replication in tumor and concomitant lymphocyte/neutrophil trafficking (SITC 2018). 2 other studies suggested greater efficacy and higher IFNβ levels with IV administration. Longer infusion durations were reported to mitigate infusion reactions (IRRs) for another oncolytic. Methods: We studied 3 different infusion durations of VV1 monotherapy at the recommended phase 2 IV dose (1.7 x 1010 TCID50) in patients with advanced solid tumors. Endpoints included safety, preliminary anti-tumor activity, viral titers, IFNβ PD and shedding. Patients received IV VV1 once on D1 and were monitored for DLT over 21 days with efficacy assessments every 6 weeks. IRRs were classified using Lee 2014 criteria for CRS as either constitutional symptoms only (G1) or involving hypotension (G2). Results: 18 patients were treated at 30, 60 and 180-minute durations (n = 7, 5 and 6, respectively). No DLTs, deaths or G3-4 related IRR AEs were observed. Most pts were female (67%), white (100%), with ECOG PS 0 (61%) and median 4 lines of prior systemic therapy (range 1-14) for colorectal (CRC; 56%), squamous cell carcinoma (11%), pheochromocytoma (11%), sarcoma (11%) or other (11%) cancers. The table shows results (number of patients) by infusion duration. Conclusions: There was no difference in safety between the 3 infusion durations, while efficacy and PD markers suggested better anti-tumor effect with 30-minute infusion. VV1 is safe for caregivers, with no viral shedding. Part 3 of this study will now treat CRC patients with VV1 in combination with a checkpoint inhibitor (avelumab). A 5-arm phase 2 basket study in combination with cemiplimab is proceeding with 30-minute infusions. Clinical trial information: NCT02923466 . [Table: see text]

Study EV-103: Durability results of enfortumab vedotin plus pembrolizumab for locally advanced or metastatic urothelial carcinoma

5044

Background: Platinum chemotherapy is the standard for patients (pts) with metastatic urothelial carcinoma (mUC) in the first line (1L) setting. PD-1/PD-L1 inhibitors, such as pembrolizumab (P), have shown promising durability in this setting for PD-L1 high patients. Enfortumab vedotin (EV) is an antibody-drug conjugate that delivers the microtubule-disrupting agent MMAE to cells expressing Nectin-4, which is highly expressed in UC. EV recently received FDA accelerated approval based on tumor response rates for adults with locally advanced or mUC who have previously received a PD-1/PD-L1 inhibitor and a platinum-containing chemotherapy. EV is investigational in the 1L setting. Initial EV + P data were previously presented (Hoimes ESMO 2019); this provides durability data and an update on safety/ORR. Methods: This multicohort study (NCT03288545) evaluated the safety/activity of EV + P. We report a cohort of 1L cisplatin-ineligible patients treated with EV 1.25 mg/kg + P. In each 3-week cycle, EV was administered on Days 1 and 8 and P on Day 1. The primary endpoint was safety/tolerability; secondary objectives included determination of recommended EV dose, ORR, DCR, DOR/PFS per RECIST v1.1, and OS. Results: As of 8 Oct 2019, 45 1L or previously untreated mUC pts (median age 69 yr [51–90]) received a median of 9 (range 1-22) cycles of EV + P. The most common treatment-emergent adverse events (AE) were fatigue (58%, 11% ≥G3), alopecia (53%), and peripheral sensory neuropathy (53%, 4% ≥G3). One pt died due to an AE reported as related (multiple organ failure). With a median follow-up of 11.5 mo, confirmed investigator-assessed ORR was 73.3% (95% CI, 58.1, 85.4) including 15.6% CRs; DCR was 93.3%. The ORR in pts with liver metastasis was 53.3% (8/15). The ORR in pts with available PD-L1 status was 78.6% in PD-L1 high (11/14) and 63.2% in PD-L1 low (12/19). Of the 33 responders, 18 (55%) have ongoing responses including 11 responses beyond 10 months. The median DOR was not reached (range 1.2 to 12.9+ mo); the 12-month DOR rate was 53.7% (95% CI, 27.4, 74.1). The median PFS was 12.3 mo (95% CI, 7.98, -); the 12-month PFS rate was 50.1% (95% CI, 33.0, 65.0). The median OS was not reached (range 0.66 to 19.2+ mo); the 12-month OS rate was 81.6% (95% CI, 62.0, 91.8). Conclusions: In 1L cisplatin-ineligible pts with mUC, EV + P, a potential platinum free option, demonstrates promising activity and durability, with a manageable safety profile. Further evaluation of EV + P in mUC and muscle-invasive UC is ongoing. Clinical trial information: NCT03288545 .

CD68+ tumor-associated myeloid cells as the target of adenosine-induced gene products and predictor of response to adenosine blockade with ciforadenant (cifo) in renal cell cancer (RCC)

5025

Background: Adenosine in the tumor microenvironment (TME) is immunosuppressive and may play a role in resistance to immunotherapy. We described an adenosine induced gene expression signature (AS, Fong, Cancer Disc 2020) that correlates with response to therapy with cifo, an adenosine A2A receptor antagonist, as monotherapy or in combination with atezolizumab in refractory RCC. These genes express chemokines that signal through CCR2 and CXCR2 to recruit myeloid cells including immunosuppressive tumor associated-M2 macrophages, which are thought to mediate resistance to anti-PD(L)1 treatment. We now identify tumor infiltrating CD68+ myeloid cells as the effector cell for adenosine mediated immunosuppression. Methods: 82 RCC pts have been treated in an ongoing Phase 1/1b trial evaluating cifo (100mg po bid) monotherapy or combination with atezolizumab (840mg IV q 2 weeks). Tumor biopsies, obtained at screening and on therapy, are available for analysis in 32 pts to date. RNA expression was measured in tumors using Nanostring. Immunohistochemistry (IHC) for CD68 was performed on biopsies with CD68+ tumors defined as > 4% tumor area containing CD68+ cells. Results: Pt characteristics are median age 63; median prior therapies 3, with 72% failing prior anti-PD(L)1. Gene expression of M2 markers consisting of CD68 (p = 0.0008) and CD163 (p = 0.03) was higher in baseline samples from AS+ compared to AS- pts. By IHC, 10 pts had CD68+ cells infiltrating the tumor; 9 of 10 AS+. Tumor regression was observed in 6 of 10 CD68+ pts (N = 3 monotherapy and 3 combination) including 4 partial responses (PR, RECIST). No PRs and 2 minor responses were seen in 22 pts who were CD68- (p < 0.005). Median time to progression was not reached for CD68+ vs 2 mo for CD68-. Paired biopsies showed a significant reduction in infiltrating CD68+ cells (p = 0.03) with treatment including 2 of 2 evaluable PRs. Conclusions: Adenosine immunosuppression is mediated by M2 macrophages, which can be reversed by cifo. Enumerating tumor infiltrating CD68+ cells may be a valuable biomarker for identifying pts that will respond to adenosine blockade. Clinical trial information: NCT02655822 .

Study EV-103: New randomized cohort testing enfortumab vedotin as monotherapy or in combination with pembrolizumab in locally advanced or metastatic urothelial cancer

TPS5092

Background: Cisplatin-based chemotherapy is the standard for first-line (1L) patients (pts) with locally advanced/metastatic urothelial cancer (LA/mUC). PD-1/PD-L1 inhibitors have promising durability of responses but 1L use is restricted to pts ineligible for cisplatin-containing therapy and whose tumors express PD-L1 (CPS ≥10) or pts ineligible for platinum-containing chemotherapy regardless of PD-L1 status. Enfortumab vedotin (EV), an antibody-drug conjugate, delivers the microtubule-disrupting agent monomethyl auristatin E to cells expressing Nectin-4, which is highly expressed in UC. EV recently received FDA accelerated approval based on tumor response rates for adults with LA/mUC who have previously received a PD-1/PD-L1 inhibitor and a platinum-containing chemotherapy. In the ongoing phase 1b/2 study EV-103/KEYNOTE-869 (NCT03288545), the safety and antitumor activity of EV are investigated as monotherapy (mono) (for the first time in the 1L setting) and in combination with PD-1 inhibitor pembrolizumab (P) +/- chemotherapy in UC. An initial analysis of EV (1.25 mg/kg) + P (200 mg) (both drugs in investigational use here) in this study showed a 73.3% confirmed ORR in 45 1L cisplatin-ineligible LA/mUC pts (dose-escalation + expansion Cohort A) (Rosenberg ASCO 2020). Methods: A new Cohort K randomized 1:1 to 1.25 mg/kg EV mono or 1.25 mg/kg EV + 200 mg P provides additional information on EV + P and the contribution of activity from EV in cisplatin-ineligible pts with LA/mUC in the 1L setting. This cohort will enroll 150 adults (≥18 years) with LA/mUC and measurable disease per RECIST v1.1, and exclude pts with prior systemic treatment for LA/mUC, active CNS metastases, ongoing sensory or motor neuropathy (Grade ≥2), or uncontrolled diabetes. Cisplatin-ineligibility in this study is based on ≥1 of the following: ECOG of 2, creatinine clearance of ≥30 and < 60 mL/min, or hearing loss/dysfunction. In each 3-week cycle of this study, EV is administered on days 1 and 8, and P on day 1. The primary endpoint is ORR per RECIST v1.1 by BICR. Secondary endpoints include ORR per RECIST v1.1 by investigator assessment, DOR, DCR, PFS per RECIST v1.1 by BICR and investigator assessment, OS, safety, and tolerability. Sample size is not based on power calculation for formal hypothesis testing but is selected based on ORR estimate precision based on 95% CIs. Efficacy is summarized by treatment arm with no formal statistical comparisons between arms. The study opened in Oct 2017. Cohort K opened in Jan 2020. Clinical trial information: NCT03288545 .

Outcomes of patients (pts) with metastatic urothelial carcinoma (mUC) following discontinuation of enfortumab-vedotin (EV): Emergence of a new unmet need

5048

Background: Enfortumab vedotin (EV) is an antibody drug conjugate recently approved to treat mUC following prior platinum and PD1/L1 inhibitors. The outcomes and patterns of therapy of pts following discontinuation of EV has yet to be studied. We investigated outcomes of pts who completed EV treatment for mUC at multiple institutions in order to identify benchmarks for evaluation of new agents following EV. Methods: Clinical data were obtained from mUC patients who had completed EV treatment from collaborating academic institutions. Descriptive stats were performed to describe the overall dataset and compare patient characteristics and outcomes of those who went on to receive further treatment post-EV and those who did not. Results: Data were available for 63 patients from 6 collaborating institutions: DFCI, University of Michigan, University of Washington, Moffitt Cancer Center, INT Milan and University of Miami. 17 (27%) were female and 46(73%) were male. The median age was 68 (range 43-83. The primary site of malignancy included bladder, upper tract, and other in 43 (68%), 19 (30%), and 1pt (.02%), respectively. The histologies included pure UC and mixed predominant UC in 49 (78%), and 14 pts (22%), respectively. 32 pts (51%) received further therapy after EV and 31pts (49%) did not. Longer duration of prior EV therapy was associated with receipt of post-EV therapy (p=0.0437). Treatments received post-EV were: trial therapy (n=14), PD1/L1 inhibitor (n=7), pemetrexed (n=4), taxane (n=3), carboplatin (n=2) and unknown in 2 pts. Objective response was observed in 3 of 32 pts (9.4%) who received therapy post-EV. The median duration of time from end of EV to death was 24 weeks. The median overall survival (OS) of those who received post-EV therapy and did not receive post-EV therapy was 37.5 weeks and 12 weeks, respectively. Conclusions: Outcomes of mUC following discontinuation of EV are dismal with only 51% receiving subsequent therapy. This study identifies an unmet need setting and establishes benchmarks for the interpretation of activity of new agents evaluated following EV.

In vivo antitumor activity by dual stromal and tumor-targeted oncolytic measles viruses

The tumor stroma acts as a barrier that limits the efficacy of systemically administered oncolytic viruses (OV). We previously demonstrated that stromal-selective, retargeted oncolytic measles viruses (MVs) delay in vivo tumor progression. To further characterize the contribution of stromal targeting to MV's overall in vivo efficacy in an experimental cancer model, a dual targeted oncolytic measles virus (MV-CD46-muPA) able to simultaneously infect murine stromal (via murine uPAR) and human cancer (via CD46) cells was developed. MV-CD46-muPA infected, replicated, and induced cytotoxicity in both murine and human cancer cells. Viral infection was successfully transferred from stromal to tumor cells in vitro, leading to tumor cell oncolysis. Systemic administration of MV-CD46-muPA led to improved antitumor effects in colon (HT-29) cancer xenografts compared to vehicle or CD46 only targeted MVs. These effects were associated with improved tumor viral deposition, increased apoptosis, and decreases in murine stromal endothelial cells and fibroblasts. MV-CD46-muPA modulated cell cycle, survival, proliferation, and metabolic pathways, as determined by functional proteomic analysis of treated tumors. The above findings further validate the concept that dual stromal and tumor cell viral targeting enhances the therapeutic effects of systemically administered OVs and support further preclinical and clinical development of stromal directed virotherapies.

Phase I/II study of the oral HIF-2 α inhibitor MK-6482 in patients with advanced clear cell renal cell carcinoma (RCC)

611

Background: Hypoxia-inducible factor (HIF)-2α is a transcription factor that is a key oncogenic driver in RCC. MK-6482 is a first-in-class small molecule HIF-2α inhibitor that blocks the heterodimerization of HIF-2α with HIF-1β and induces regression in mouse xenograft RCC models. Methods: Pts with advanced ccRCC who had received at least 1 prior therapy were enrolled in an expansion cohort from the first-in-human phase 1/2 study of MK-6482 in advanced solid tumors (NCT02974738). Pts were administered 120 mg of MK-6482 orally once daily. Primary end point: safety. Key secondary end points: ORR, duration of response (DOR), and PFS. Results: Fifty-five pts were enrolled in the dose expansion cohort. Median (range) number of prior therapies was 3 (1-9); 67% received anti–PD-1 and anti-VEGF agents. Five pts (9%) were favorable risk, 40 (73%) were intermediate risk, and 10 (18%) were poor risk by IMDC criteria. With a median follow-up of 13 mo the most common all-grade, all-cause AEs > 30% were anemia (75%), fatigue (67%), dyspnea (47%), nausea (33%), and cough (31%). Anemia (26%) and hypoxia (15%) were the most common grade 3 AEs. No grade 4/5 drug-related AEs were observed. ORR was 24% with 13 confirmed PRs. Thirty-one pts (56%) had SD, with a disease control rate (CR+PR+SD) of 80%. Thirty-five of 52 (67%) pts with baseline and postbaseline assessments had tumor shrinkage. Median DOR was not reached; 81% of pts had response ≥6 mo per Kaplan-Meier estimate. Sixteen pts (29%) continued treatment beyond 12 mo. By IMDC risk, 2/5 pts with favorable risk had PR (ORR = 40%), 10/40 with intermediate risk had PR (ORR = 25%), and 1/10 with poor risk had PR (ORR = 10%); disease control rate was 100%, 80%, and 70%, respectively. Median PFS for the total population was 11.0 mo; the 12 mo PFS rate was 49%. Median PFS for favorable, intermediate, and poor IMDC risk was 16.5, 11.0, and 6.9 mo, respectively. As of May 15, 2019, 30 pts (55%) discontinued due to PD, 2 (4%) due to AEs. Sixteen pts (29%) had treatment ongoing. Conclusions: MK-6482 is well tolerated with a favorable safety profile and demonstrated promising single-agent activity in heavily pretreated pts with ccRCC across IMDC risk groups. A phase 3 trial in a similar population is planned. Clinical trial information: NCT02974738.

Study EV-103: Preliminary durability results of enfortumab vedotin plus pembrolizumab for locally advanced or metastatic urothelial carcinoma

441

Background: Platinum chemotherapy is the standard for patients (pts) with metastatic urothelial carcinoma (mUC) in the first line (1L) setting. In cisplatin-ineligible pts, gem/carbo is a standard therapy, but is poorly tolerated with limited durability and survival. PD-1/PD-L1 inhibitors, such as pembrolizumab (P), have shown promising durability in this setting for PD-L1 high patients. Enfortumab vedotin (EV) is an antibody-drug conjugate that delivers the microtubule-disrupting agent MMAE to cells expressing Nectin-4, which is highly expressed in UC. EV has shown activity in previously treated mUC. Initial EV + P data were previously presented (Hoimes ESMO 2019); this provides first durability data and an update on safety/ORR. Methods: This multicohort study (NCT03288545) evaluated the safety/activity of EV + P. We report a cohort of 1L cis-ineligible patients treated with EV 1.25 mg/kg + P. In each 3-week cycle, EV was administered on Days 1 and 8 and P on Day 1. The primary endpoint was safety/tolerability; secondary objectives included determination of recommended EV dose, ORR, DCR, DOR/PFS per RECIST v1.1, and OS. Results: As of 8 Oct 2019, 45 mUC pts (median age 69 yr [51–90]) received a median of 9 (range 1-22) cycles of EV + P. The most common treatment-emergent adverse events (AE) were fatigue (58%, 11% ≥G3), alopecia (53%), and peripheral sensory neuropathy (53%, 4% ≥G3). One pt died due to an AE reported as related (multiple organ failure). With a median follow-up of 11.5 mo, confirmed investigator-assessed ORR was 73.3% (95% CI, 58.1, 85.4) including 15.6% CRs; DCR was 93.3%. The ORR in pts with liver metastasis was 53.3% (8/15). The ORR in pts with available PD-L1 status was 78.6% in PD-L1 high (11/14) and 63.2% in PD-L1 low (12/19). Of the 33 responders, 18 (55%) have ongoing responses including 11 responses beyond 10 months. The median DOR was not reached (range 1.2 to 12.9+ mo). The median PFS was 12.3 mo (95% CI, 7.98, -). Conclusions: In 1L cis-ineligible pts with mUC, EV + P, a potential platinum free option, demonstrates promising activity and durability, with a manageable safety profile. Further evaluation of EV + P in mUC and muscle-invasive UC is ongoing. Clinical trial information: NCT03288545.

Adenosine receptor blockade with ciforadenant +/- atezolizumab in advanced metastatic castration-resistant prostate cancer (mCRPC)

129

Background: Adenosine, generated by the ectonucleotidase CD73, mediates immunosuppression within the tumor microenvironment by triggering adenosine 2A receptors (A2AR) on immune cells. Tumor CD73 expression may be prognostic in prostate cancer. We evaluated the clinical activity of adenosine blockade using A2AR antagonist, ciforadenant, with or without the anti-PDL-1 antibody, atezolizumab (atezo), in advanced mCRPC patients (pts) in an ongoing phase 1 trial. Methods: Eligibility required measurable disease and up to 5 prior systemic therapies. Prior anti- PD-(L)1 was allowed. Ciforadenant was administered orally BID as monotherapy at 50-200mg or 100mg in combination with atezo 840mg IV Q 2 weeks (wks). Safety and efficacy were evaluated by CTCAE4, RECIST1.1 and PCWG2. Serum was obtained for measurement of cytokines. Results: Of 33 enrolled pts, 10 received ciforadenant monotherapy and 23 in combination with atezo. As of 10/21/19, 14 pts are evaluable for response and described further. Median prior therapies is 3 (range 2-6) with median follow-up 10.8 (4-33) wks. Metastatic burden included 4 node only, 2 bone plus node, and 8 visceral metastases. Five pts experienced tumor regression: 2 ciforadenant monotherapy (tumor reductions 12%, 17%); and 3 combination (tumor reductions 4%, 27%, 42%). The pt with a partial response had PSA decline from 98 ng/mL to <1. Eight pts had stable disease (SD) for a clinical benefit rate (SD + PR) of 8/14 (57%). Median duration of disease control was 24 wks. Study treatment was well tolerated with two Gr3/4 adverse events (AEs) of fatigue (1) and anorexia (1). The most common Gr1/2 AEs were fatigue and nausea. Serum TNFα levels increased by 4-8 wks on therapy in 12/13 pts. Baseline levels of soluble VCAM-1, which has been implicated in metastatic spread/more aggressive disease, were higher in pts with tumor regression (771 ± 109 ng/mL, n=4) than pts with tumor growth (544 ± 62 ng/mL, n=5, p<0.05). Conclusions: Results from this phase 1 study show mCRPC can be sensitive to A2AR blockade with ciforadenant. Cytokine changes provide evidence of treatment-induced inflammatory response, which may predict efficacy. Data on all 33 enrolled pts will be presented. Clinical trial information: NCT02655822.

Immune modulation after Toca 511 and Toca FC treatment of colorectal cancer patients

186

Background: Toca 511 (vocimagene amiretrorepvec) is a cancer-selective, retroviral replicating vector encoding yeast cytosine deaminase that converts 5-fluorocytosine (5-FC) into 5-fluorouracil in the tumor microenvironment (TME). In animal models, Toca 511 and 5-FC kill dividing cancer and nearby immunosuppressive cells, leading to antitumor immune activity. A Phase 1 study of Toca 511 & Toca FC (extended-release 5-FC) in patients with recurrent high grade glioma revealed results consistent with this proposed mechanism. A Phase 3 trial is ongoing. Methods: Toca 6 (NCT02576665) is a Phase 1b, single-arm, multicenter study designed to investigate immunological changes after Toca 511 & Toca FC treatment in patients with advanced solid tumors, including colorectal cancer (CRC). Patients received intravenous (IV) Toca 511 for 3 days, and underwent biopsy of metastatic tumor before and ~ 4 weeks after starting oral Toca FC. Toca FC was repeated every 4-6 weeks. Peripheral blood mononuclear cells and tumor biopsies were evaluated for treatment related immune responses. Results: 17 CRC patients with a median 5 lines of prior chemotherapy were enrolled. At last data cut-off, 9 patients were alive and the median overall survival was 9.4 months. A patient receiving concomitant panitumumab had a partial response. IV Toca 511 led to viral expression in tumor, which decreased post-Toca FC while maintaining a reservoir of virus in the remaining tumor. T cells shifted from naïve to effector phenotypes, CD4 memory T cells expanded, and/or B cells increased after Toca FC treatment in 36% of patients. Marked changes in tumor infiltrating cells (CD11b myeloid cells, Tregs, exhausted T cells and CD8 T cells) occurred after Toca FC treatment. Treatment has been generally well tolerated. We also plan to report insights gained from RNA analysis of TME and update on clinical finding. Conclusions: Clinical data suggest a signal of activity in these heavily pretreated CRC patients warranting further exploration. IV Toca 511 administration showed viral infection of CRC metastatic tumor. Toca 511 & Toca FC may be associated with T cell mediated immune activity in peripheral blood and metastatic tumor, consistent with pre-clinical data in multiple tumor types. Clinical trial information: NCT02576665.

Survey results from a patient’s perspective during a phase I/research clinic visit

216

Background: The University of Miami’s Phase I Program is South Florida’s only academic Phase I center dedicated to drug development for cancer patients. On April 2018, Sylvester Comprehensive Cancer Center opened the Phase I/Experimental Therapeutics (ET) Clinic dedicated to research patients enrolled in Phase I clinical trials and established a multi-disciplinary care team. As Phase I clinical trials are evolving, it is necessary to improve on the patient experience as it pertains to research care. Methods: Using a Likert-type scale, dual language survey (English and Spanish), patients were asked 11 questions about the Phase I/ET Clinic visit ranging from the beginning of their Phase I clinical trial enrollment all the way to provider care during the visit. The survey was conducted from January 2019-April 2019 through a secure, HIPAA compliant online Research Electronic Data Capture software (REDCap). Results: Of the 30 patients that were approached, 26 responded (Renal 26.9%, Myelofibrosis 19.2%, Bladder 15.4%, Head and Neck 7.7%, Acute Myeloid Leukemia 15.4%, Myelodysplastic Syndrome 7.7%, and Other 7.7%). Our results found that 100% of research patients would recommend a Phase I clinical trial to another participant. In addition, 96.2% of patients felt there was continuation of their care through their clinical trial process. As a note, 19.2% of patients positively recognized a Phase I provider including Nurse Practitioners (NPs) and physicians. Of these 19.2% of patients, 50% praised an NP in the free text area of the survey. Lastly, 42.3% of patients positively mentioned the team support received in the Phase I Clinic in the free text area of the survey. Conclusions: Our conclusion based on survey results show that having committed providers and clinic space for research patients on a Phase I clinical trial provided an overall positive and personalized experience. Additionally, the survey reflects on how patients are more inclined to refer to a clinical trial due to a good experience. Future directions should look at developing a similar clinic for all phases of research considering the exceptional patient feedback emphasizing on provider care.

Abstract 5103: The dark cancer kinome - untapped opportunities for the development of novel drugs

Kinases are firmly established drug targets in cancer. There are currently 44 FDA approved kinase drug and hundreds of compounds are in clinical development. However, less than 10% of the Kinome is currently targeted and a large proportion is considered understudied by the NIH Illuminating the Druggable Genome Program (https://druggablegenome.net/). No small molecule inhibitors are known for these “dark” proteins, yet many may be opportune novel cancer targets.We developed a computational pipeline to identify and prioritize understudied kinases as cancer drug targets. We analyzed the complete set of tumors in The Cancer Genome Atlas (TCGA). For 33 different cancers we performed differential expression analysis and identified 39 dark kinases that exhibit significant upregulation in at least four types. Using co-expression analysis we built functional networks prioritizing drug targets. To identify small molecules that reverse their expression levels, we leveraged transcriptional response signatures obtained from dozens of human cancer cell lines exposed to tens of thousands of small molecules from the Library of Integrated Network-based Cellular Signatures (LINCS). To identify small molecules that directly bind to and inhibit dark kinases, we have have combined an advanced AI (artificial intelligence) model trained on activity data from across the Kinome with structure-based simulations.Using the computational pipeline, we identified the dark Ca2+/Calmodulin dependent kinase PNCK as the most differentially overexpressed kinase in kidney cancer patients. Our analyses have demonstrated statistically significant correlation between PNCK mRNA levels and various clinical and pathological outcomes, including histologic grade, clinical staging and overall survival. We have confirmed high levels of PNCK expression in 5 renal cell carcinoma cell lines (Caki-1, ACHN, 786-O, A704 and A498). Knockdown and overexpression studies have suggested PNCK and the CaMK pathway may contribute to cellular proliferation and cell cycle progression. We have applied our AI-based screening pipeline to a library of &gt;20 million commercially available compounds and confirmed three PNCK inhibiting chemotypes. In summary, using a novel computational pipeline, we have identified and experimentally validated PNCK as a prospective novel drug target in an understudied pathway that is highly upregulated in kidney cancer. We identified first in class small molecules that target this previously dark kinase as prospective starting points for optimization into a clinical candidate.

Citation Format: Derek J. Essegian, Rimpi Khurana, Vasileios Stathias, Valery Chavez, Jaime R. Merchan, Stephan Schürer. The dark cancer kinome - untapped opportunities for the development of novel drugs [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5103.

Abstract CT090: Rational design of an oncolytic virus permits use of interferon beta as a pharmacodynamic marker for clinical application

Introduction. Voyager-V1 (VV1) is an oncolytic vesicular stomatitis virus engineered to express human interferon beta (IFNβ) to enhance cellular antitumor immune responses and tumor selectivity. VV1 also contains the human sodium iodide symporter (NIS) as an imaging gene. We report here the novel use of virus-encoded IFNβ as a PD marker using correlative data from three Phase I trials of VSV-IFNβ-NIS in patients with refractory cancers (n=46).

Methods. 46 patients with solid tumors (n=34) and hematological malignancies (n=12) received 1 dose of VV1 either intratumorally (ITu) or intravenously (IV) at doses ranging from 3 x 106 to 5 x 1010 TCID50. Plasma IFNβ levels were collected pre-treatment, 4 hours post-infusion, Day 2 (24-hour), Day 3, 8, 15 and 29 (IT only). Samples were processed using a standard IFNβ specific ELISA kit.

Results. ITu dose escalation is complete with 27 patients treated and no DLTs. IV escalation is ongoing at 5 x 1010 TCID50 with 19 patients treated to date. In the ITu study, plasma IFNβ levels at 24h were undetected at the lowest dose levels (up to 1 x 107 TCID50), and became detectable from 3 x 107 TCID50. In the IV patients, IFNβ was detectable at all dose levels (5 x 109 through 5 x 1010 TCID50) with the highest peak and longest duration in a patient with metastatic endometrial cancer coincident with shrinkage of multiple tumors. The IFNβ produced by virus-infected cells can be differentiated from the acute innate antiviral responses by magnitude of response and AUC as the majority of the inflammatory cytokines returned to baseline by 48h. Peak IFNβ levels were variable between patients, likely reflecting heterogeneity in tumor susceptibility to VV1, ranging from 1.4pg/mL to 656pg/mL across 6 patients (mean 153pg/ml) at the highest ITu dose. Plasma IFNβ 24 hours post-therapy of &gt;20pg/mL appears to predict for RECIST 1.1-evaluated SD vs PD, p=0.048 in the ITu patients. Peak IFNβ ranged from 18 to 1700 pg/mL across 9 patients (mean=442pg/ml) at 1.7 x 1010 in the IV study. Peak IFNβ was highest in two cases of endometrial cancer (1500 and 1700 pg/ml). The patient with the highest IFNβ levels on the IV trial showed 16.7% tumor shrinkage at the first tumor evaluation. SPECT imaging, which shows location of viral replication, was positive in 50% of ITu injected tumors, also validating of VV1 infection of target cells. To date, SPECT images were negative in the IV trial despite IFNβ positivity, reflecting IFNβ as a more sensitive PD marker of viral infection. IHC staining of tumor biopsies collected pre-treatment and 1 month after VSV showed increased numbers of CD3, CD8, CD68, PDL1 or PD1 in some injected or noninjected tumors. Other immune markers and tumor gene signatures are also being evaluated.

Conclusions. Plasma IFNβ has emerged as a simple and convenient biomarker of viral replication in tumors. IFNβ will be used in future studies as a PD marker to assess the impact of immune-modulating combination drugs with VV1.

Citation Format: Timothy P. Cripe, Jamie Bakkum-Gamez, Jaime R. Merchan, Martha Q. Lacy, Manish R. Patel, Steven Powell, James Strauss, Lianwen Zhang, Toshie Sakuma, Memy Diaz, Nandakumar Packiriswamy, Deepak Upreti, Bethany Brunton, Dragan Jevremovic, Stephen J. Russell, Alice Bexon, Kah-Whye Peng. Rational design of an oncolytic virus permits use of interferon beta as a pharmacodynamic marker for clinical application [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT090.

Immunobiology, preliminary safety, and efficacy of CPI-006, an anti-CD73 antibody with immune modulating activity, in a phase 1 trial in advanced cancers

2505

Background: CPI-006 inhibits CD73, a nucelotidase that converts AMP to adenosine and functions as a lymphocyte adhesion molecule. CPI-006 is a humanized IgG1 FcγR binding-deficient antibody that binds to CD73+ T and B lymphocytes leading to activation of B cells and expression of CD69. This study investigates the immunobiology, safety, and efficacy of CPI-006 monotherapy and in combination with CPI-444, an adenosine A2A receptor (A2AR) antagonist (NCT03454451). Methods: Patients with relapsed solid tumors were treated in a 3 + 3 escalation study with 1, 3, 6 or 12 mg/kg CPI-006 (Q3w IV infusion) monotherapy or in combination with CPI-444 (100 mg, PO, BID). Flow cytometry was performed on blood samples for lymphocyte subset analysis and receptor occupancy. Results: 17 patients were enrolled; 11 monotherapy and 6 combination. CPI-006 was associated with Grade 1 infusion reactions occuring within 30 minutes of the first infusion and were eliminated by premedication with non-steroidals. No DLTs with monotherapy or combination therapy were seen. Receptor occupancy on peripheral lymphocytes was maintained for the full dosing interval at 12 mg/kg. Pharmacodynamic effects suggesting immune modulation were observed within 1 hr of infusion at all dose levels and included a decrease in peripheral blood CD73pos B cells (mean reduction 86%, p < 0.05), increased CD73neg CD4 T cells (mean increase 37%, p < 0.01), and decreased CD8 T cells (mean reduction 20%, p < 0.01) compared to baseline. Overall, CD4:CD8 ratios were increased. Tumor regression was observed in a prostate cancer patient after 5 cycles of monotherapy at 6 mg/kg; peripheral B cells partially returned by the second cycle and reached a new homeostatic level through subsequent cycles. No change in serum immunoglobulins were observed. Conclusions: CPI-006 induces a rapid lymphocyte redistribution, including a transient reduction of circulating CD73pos B cells suggesting redistribution to lymphoid tissues, and an increased CD4:CD8 ratio, consistent with increased TH effector/memory cells in the blood. The treatment has been well-tolerated, and there is early evidence of anti-tumor activity of CPI-006 monotherapy. Clinical trial information: NCT03454451.

A phase I/Ib multicenter study to evaluate the humanized anti-CD73 antibody, CPI-006, as a single agent, in combination with CPI-444, and in combination with pembrolizumab in adult patients with advanced cancers

TPS2646

Background: CD73 expression is elevated in tumors and contributes to increasing levels of immunosuppressive adenosine in the tumor microenvironment. CD73 knockout mice exhibit reduced tumor growth and resistance to experimental metastasis. Inhibition of CD73 activity with an anti-CD73 antibody blocks adenosine production, shown to inhibit tumor growth in syngeneic models. CPI-006 is a humanized IgG1 FcγR binding-deficient anti-CD73 antibody now being investigated in this Phase 1/1b multicenter, open label trial as single agent (SA) or combination with CPI-444, an oral, small molecule, selective A2aR antagonist or in combination with pembrolizumab, an anti-PD1 indicated for the treatment of patients across a number of malignancies (NCT03454451). Methods: Up to 462 subjects will be enrolled at approximately 35 sites in the US, Canada and Australia. Eligible patients must have: non-small cell lung, renal cell carcinoma, urothelial bladder, cervical, colorectal, ovarian, pancreatic, prostate, head and neck, triple-negative breast, endometrial, select sarcomas and non-Hodgkin lymphoma malignancies relapsed, refractory or intolerant to 1 to 5 standard therapies; aged ≥ 18 yo; adequate organ function and measurable disease. The objectives of the study are 1) evaluate the safety and tolerability of SA CPI-006, in combination with CPI-444 and in combination with pembrolizumab, 2) evaluate the pharmacokinetics of each regimen and 3) identify potential biomarker signals predictive of response. Study design in table. Study Design. Clinical trial information: NCT03454451. [Table: see text]

An open label, multicenter, phase I/II study of RP1 as a single agent and in combination with PD1 blockade in patients with solid tumors

TPS2671

Background: RP1 is an attenuated oncolytic HSV-1 that expresses a fusogenic glycoprotein from gibbon ape leukemia virus (GALV-GP R-) and GM-CSF. RP1 induces potent GALV-GP R- enhanced immunogenic cell death and host anti-tumor immunity in murine tumor models and increases PD-L1 expression. This clinical trial (NCT03767348) was designed to test the hypotheses that RP1 is safe when given alone and together with nivolumab (phase 1) and has efficacy together with nivolumab in four tumor types (phase 2). Methods: The primary goals of this clinical trial in a total of ~150 patients are to define the safety profile of RP1 alone and together with nivolumab, determine the recommended phase 2 dose (phase 1), and then in four phase 2 cohorts, to determine objective response rate in patients with melanoma, non-melanoma skin cancer, urothelial carcinoma and MSI-H solid tumors. Secondary objectives include duration of response, CR rate, PFS, viral shedding, and immune biomarker analysis. Patients with advanced cancer who failed prior therapy were eligible for the phase I component. In Phase 2 patients with histologic diagnoses of the four tumor types (N=30 for each) and who meet safety criteria for nivolumab treatment are eligible. Prior treatment with checkpoint blockade is not allowed except for the melanoma cohort. In the phase 1 portion patients are treated by intra-patient dose escalation of virus (range, 104 - 108 PFU) by intratumoral injection every two weeks for 5 total doses followed by 12 patients dosed 8 times at the RP2D in combination with nivolumab. Phase 1 patients were divided into two groups based on presence of clinically accessible lesions amenable to direct injection or those with visceral/deep lesions requiring image guidance for injection. In the phase 2 portion patients will receive the RP2D for eight injections and nivolumab will be given starting with the second RP1 injection. For the phase 1 portion, a modified 3+3 dose escalation design is used to assess safety and in the phase 2 portion, statistical analysis will be performed using a two-stage three-outcome optimum design with objective responses determined by RECIST criteria. As of February 11, 2019, 27 patients have been enrolled. Clinical trial information: NCT03767348.

Axitinib plus pembrolizumab in patients with advanced sarcomas including alveolar soft-part sarcoma: a single-centre, single-arm, phase 2 trial

BACKGROUND

VEGF promotes an immunosuppressive microenvironment and contributes to immune checkpoint inhibitor resistance in cancer. We aimed to assess the activity of the VEGF receptor tyrosine-kinase inhibitor axitinib plus the anti-PD-1 immune checkpoint inhibitor pembrolizumab in patients with sarcoma.

METHODS

This single-centre, single-arm, phase 2 trial was undertaken at a tertiary care academic medical centre in Miami, FL, USA, and participants were recruited from all over the USA and internationally. Patients were eligible if they were aged 16 years or older, and had histologically confirmed advanced or metastatic sarcomas, including alveolar soft-part sarcoma (ASPS); measurable disease with one site amenable to repeated biopsies; an ECOG performance status of 0-1; and progressive disease after previous treatment with at least one line of systemic therapy (unless no standard treatment existed or the patient declined therapy). The first five patients were enrolled in a lead-in cohort and were given axitinib 5 mg orally twice daily and pembrolizumab 200 mg intravenously for 30 min on day 8 and every 3 weeks for cycles of 6 weeks for up to 2 years. Thereafter, patients received escalating doses of axitinib (2-10 mg) plus flat dose pembrolizumab according to the schedule above. The primary endpoint was 3-month progression-free survival. All patients were evaluable for survival and safety analyses. This study is registered with ClinicalTrials.gov, number NCT02636725, and is closed to accrual.

FINDINGS

Between April 19, 2016, and Feb 7, 2018, of 36 patients assessed for eligibility, 33 (92%) were enrolled and given study treatment (intention-to-treat population and safety population), 12 (36%) of whom had ASPS. With a median follow-up of 14·7 months (IQR 10·1-19·1), 3-month progression-free survival for all evaluable patients was 65·6% (95% CI 46·6-79·3). For patients with ASPS, 3-month progression-free survival was 72·7% (95% CI 37·1-90·3). The most common grade 3 or 4 treatment-related adverse events included hypertension (five [15%] of 33 patients), autoimmune toxicities (five [15%]), nausea or vomiting (two [6%]), and seizures (two [6%]). Serious treatment-related adverse events occurred in seven (21%) patients, including autoimmune colitis, transaminitis, pneumothorax, haemoptysis, seizures, and hypertriglyceridemia. There were no treatment-related deaths.

INTERPRETATION

Axitinib plus pembrolizumab has manageable toxicity and preliminary activity in patients with advanced sarcomas, particularly patients with ASPS, warranting further investigation in randomised controlled trials.

FUNDING

Merck, Pfizer, American Cancer Society, and Sylvester Comprehensive Cancer Center.

Mature results from EV-101: A phase I study of enfortumab vedotin in patients with metastatic urothelial cancer (mUC)

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Background: Enfortumab vedotin (EV) is an antibody–drug conjugate that delivers MMAE, a microtubule disrupting agent, to tumors expressing Nectin-4, a protein found on most urothelial cancers. Preliminary results of the EV-101 study (NCT02091999) suggest EV is active and tolerable. Methods: Patients with mUC treated with ≥1 prior chemotherapy, or those ineligible for cisplatin, received EV 1.25 mg/kg on Day 1, 8, and 15 every 28 day cycle. The primary objective was tolerability; antitumor activity (ORR per RECIST v1.1), assessed every 8 wk, was a secondary objective. Results: As of14 Sept 2018,112 pts with mUC received EV with a median follow up of 13.4 mo. Bladder was the primary tumor site in 86 pts (77%) and 33 (29.5%) had liver metastases (LM). Nearly all pts received prior platinum chemotherapy; 89 (79.5%) received prior anti-PD(L)1. EV was well tolerated; fatigue (53%), alopecia (46%), and decreased appetite (42%) were the most commonly reported treatment-related AEs (TRAEs). Anemia (8%), hyponatremia (7%), UTI (7%), and hyperglycemia (6%) were the grade ≥3 AEs reported in ≥5% of pts regardless of attribution; 4 fatal TRAEs were reported (respiratory failure, urinary tract obstruction, diabetic ketoacidosis, multi-organ failure). Confirmed ORR was 42% (CR, n = 5; PR, n = 42). Among responders, median duration of response was 7.7 mo (95% CI 5.6, 9.6) and 23.4% of responses were ongoing with a median follow up of 11.3 mo. Estimated median PFS and OS were 5.4 mo (95% CI 5.1, 6.3) and 12.5 mo (95% CI 9.3, 16.1), respectively; OS at 1 yr was 51.8%. Similar results were seen in pts with prior anti-PD(L)1 and with LM (Table). Conclusions: Single-agent EV was generally well tolerated and provided encouraging response and survival data in a population with an unmet medical need including pts with LM, which is associated with poor prognosis. Phase 2 and 3 monotherapy studies as well as evaluation of combination therapies are ongoing. Clinical trial information: NCT02091999. [Table: see text]

Results from a phase I expansion cohort of the first-in-class oral HIF-2α inhibitor PT2385 in combination with nivolumab in patients with previously treated advanced RCC

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Background: The transcription factor hypoxia-inducible factor (HIF)-2α has been established as an oncogenic driver in clear cell renal cell carcinoma (ccRCC) due to underlying VHL deficiency. Activation of HIF-2α can also promote immunosuppression. In preclinical models, HIF-2α inhibition demonstrated increased efficacy in combination with checkpoint inhibitors (Han et al. AACR 2016). In a Phase 1 dose escalation/expansion trial in heavily pre-treated advanced ccRCC patients, PT2385 monotherapy was associated with variability in drug exposure with higher therapeutic exposure associated with improved anti-tumor activity (Courtney et al. JCO 2018). Methods: In the current Phase 1 expansion cohort, patients with advanced ccRCC who had received 1-3 prior therapies (including at least one VEGF(R)-targeting agent) were treated with PT2385 (800 mg PO BID) in combination with nivolumab (3 mg/kg IV Q2Weeks) to evaluate safety, efficacy, and pharmacokinetics. Results: 50 patients were enrolled. Median age was 62 with 58% ECOG 1 and 42% ECOG 2. Median number of prior therapies was 1; 42% of patients received ≥2 prior lines of therapy. The most common all-grade AEs were anemia (46%), fatigue (46%), nausea (36%), and arthralgia (30%). The most common Grade 3 AE’s were anemia (4%), fatigue (4%), and hypoxia (4%). Two Grade 4 events of elevated ALT and increased lipase/amylase were observed. As of August 31, 2018, ORR = 22% (1 CR, 10 PR). At a median follow up of 12.4 months (m), median PFS was 7.3 m for all patients. Patients who had sub-therapeutic exposures ( < 300 ng/ml) of PT2385 (n = 17) had a median PFS of 4.7 m compared to patients with therapeutic exposures of PT2385 (n = 33), who had a median PFS of 10.0 m. Conclusions: The combination of PT2385 + nivolumab was well tolerated and demonstrated promising anti-tumor activity in advanced ccRCC patients, most notably in patients who achieved therapeutic exposure of PT2385. Single agent and combination studies with PT2977, a second-generation HIF-2α inhibitor with an improved PK profile, are ongoing. Clinical trial information: NCT02293980.

Abstract CT051: Preliminary correlative and clinical data from a first-in-human (FIH) study of the intratumoral (IT) oncolytic virotherapy, Voyager-V1, in patients with solid tumors

Introduction Voyager-V1TM is derived from VSV, a bullet-shaped negative sense RNA virus with very low human seroprevalence; it is engineered to selectively replicate in and kill human cancer cells. Voyager-V1 encodes the human IFNβ gene to boost antitumoral immune responses and the thyroidal sodium iodide symporter NIS gene to permit noninvasive imaging of virus spread. FIH studies are underway via both IV and IT routes. Here we report safety and preliminary correlative data from the FIH IT study.

Methods and objectives This is a classical 3+3 phase 1 design, using escalating single IT viral doses from 3 x 106 to 3 x 109 TCID50 into one target lesion. The primary objective is safety and tolerability, monitored by committee. Other objectives include PK by RT-PCR for viral genomes, serum IFNβ levels, Tc-99m SPECT/CT imaging to monitor virus infection in injected lesions, peripheral blood immunophenotyping with 11-color flow cytometry for activation markers on T cells, T-regs, NK cells, and MDSCs, and serial biopsies to assess the tumor microenvironment (TME). IHC was performed on tumor biopsies for CD3, CD8, CD4, FoxP3, CD68, PD-1 and PDL-1 pre and post treatment in non-injected and injected lesions. CD45 staining is ongoing.

Results Dose level 3 is ongoing (n=8+). No DLTs have been observed to date. Most patients were male (75%), white (100%), with ECOG PS1 (75%) and a median of &gt;6 lines of prior systemic therapy. AEs (in 63% patients) reported as related to study drug were mild-moderate, short-lived, and consisted of G1 fever, chills, hot flashes, nausea, vomiting, hyperhidrosis and G2 fatigue. Most patients had some mild AEs (pain, bruising, subclinical pneumothorax) related to biopsy and IT injection procedures and one had an SAE related to biopsy (G2 pneumothorax). There was no difference in incidence, intensity or duration of related AEs between dose levels so far. In patients analyzed to date, at the first three dose levels of 3 x 106, 1 x 107 and 3 x 107 TCID50 (n=7), viremia and serum IFNβ were below levels of detection after IT injection. There is evidence in all patients of an increase in PD-1 expression on CD4 and CD8 T cells, suggesting T cell activation post- single virus injection. One patient at dose level 2 had increased CD4 and CD8 T cells in the peripheral blood. TME analysis revealed increased infiltration of CD3 and CD8 cells in tumors of some patients. In addition, there are changes in numbers of FoxP3 and CD68 positive cells in the injected lesions compared to the pre-treatment and non-injected lesion. Two patients at dose level 3, one with an injected adrenal metastasis of colorectal cancer and another with a chest wall lesion from a head of pancreas primary, have positive SPECT/CTs on days 3-15 showing viral replication in tumor plus concomitant lymphocyte/neutrophil trafficking in the periphery.

Conclusions IT injection of a single dose of the novel oncolytic virotherapy Voyager-V1 has proven safe at doses up to 3 x 107 TCID50. There was evidence of T cell activation with increased PD-1 expression in peripheral blood lymphocytes after a single IT injection. Tumor biopsies indicate increased lymphocyte infiltration. Two patients at the highest dose tested show signs of viral replication in the injected lesion plus evidence of systemic impact on leukocyte populations.

Citation Format: Steven Powell, Manish R. Patel, Jaime R. Merchan, Timothy P. Cripe, James Strauss, Rosa M. Diaz, Nandakumar Packiriswamy, Bethany A. Brunton, Deepak Upreti, Rehan Khan, Lukkana Suksanpaisan, Rianna Vandergaast, Stephen J. Russell, Alice S. Bexon, Kah Whye Peng. Preliminary correlative and clinical data from a first-in-human (FIH) study of the intratumoral (IT) oncolytic virotherapy, Voyager-V1, in patients with solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr CT051.

Enfortumab vedotin (EV) in patients (Pts) with metastatic urothelial carcinoma (mUC) with prior checkpoint inhibitor (CPI) failure: A prospective cohort of an ongoing phase 1 study

431

Background: EV is an ADC that selectively targets and kills cells expressing Nectin-4 by delivering a potent microtubule-disrupting agent, monomethyl auristatin E. As mUC tumors express Nectin-4 in almost all pts, the EV clinical profile was assessed in an ongoing Phase 1 study (NCT02091999) at the recommended phase 2 dose (RP2D; 1.25 mg/kg) in mUC pts with CPI failure, a population with a high unmet medical need. Methods: Pts with mUC, treated with ≥1 prior chemotherapy or who were ineligible for platinum chemotherapy, and who had disease progression after CPI therapy received an IV infusion of EV at RP2D on Days 1, 8, and 15 of each 28-day cycle. Primary endpoint was tolerability; a secondary endpoint was investigator-assessed antitumor activity per RECIST v1.1. Results: As of 2 Oct 2017, 62 pts with mUC and prior CPI failure received EV at RP2D (48 M/14 F; median age, 68 yr [range: 41–83]; ECOG 0/1 29%/71%). Primary tumor site was bladder in 73% pts; 63% pts had visceral and 27% had liver metastasis (LM). Most pts (71%) had ≥2 prior therapies in the metastatic setting, including platinum (87%) or taxanes (26%). CPI was the most recent therapy in 76% pts; time from last CPI to first EV dose was < 12 wk for 58% pts. Median treatment duration was 14.8 wk (range: 1.6–40.4); 39 pts continue treatment. Treatment-related AEs occurring in ≥30% pts were fatigue, rash, nausea, alopecia, decreased appetite and diarrhea; most grade ≤2. Grade ≥3 AE reported in ≥5% pts, regardless of attribution, was hyponatremia (6.5%). One fatal AE (respiratory failure) was possibly treatment related. Response evaluable pts (n = 54) had ≥1 post baseline scan or discontinued prior to scan. ORR (confirmed + unconfirmed) was 54% (95% CI: 39.6–67.4); 15 pts had a confirmed PR, 5 had unconfirmed PR, and 9 are pending subsequent assessment. This ORR is similar to CPI-naïve pts (59%; 95% CI: 36.4–79.3). ORR from 17 evaluable pts with LM was 41% (95% CI: 18.4–67.1). Conclusions: EV is tolerable and exhibits antitumor activity in a cohort of pts with mUC and disease progression after CPI. A phase 2 study assessing EV in this population with high unmet need has been initiated (NCT03219333; EV-201 study). Clinical trial information: NCT02091999.

The nab-paclitaxel/gemcitabine regimen for patients with refractory advanced pancreatic adenocarcinoma

The phase III MPACT trial for metastatic pancreatic cancer (PC) showed improved overall survival (OS), progression free survival (PFS) and response rates (RRs) for first-line nab-paclitaxel (Abraxane) and gemcitabine (the AG combination) compared to gemcitabine monotherapy. The safety and efficacy of the AG combination has not been systematically studied as second-line therapy or beyond for metastatic PC. We conducted an IRB-approved retrospective analysis of all patients diagnosed between September 2010 and August 2014 with advanced refractory PC that received combination treatment with AG at our institution. Demographic and survival data were extracted from the registry. Patients received nab-paclitaxel 125 mg/m² and gemcitabine 1,000 mg/m² and on days 1, 8 and 15 of a 28-day cycle with subsequent dose modifications based on tolerance. Data on 59 patients was available; the median age was 61; 55% were male; 56% received AG as second line therapy and 44% received it as third-line or beyond. Five (10%) patients had a confirmed partial response (PR), 23 (47%) had stable disease (SD) and 21 (43%) had disease progression as their best response. Among the 31 (52%) patients who received prior gemcitabine, 18 (58%) had clinical benefit; 3 had a PR and 15 had SD. The median OS was 3.9 months and the median progression-free survival was 3 months. Toxicity was similar to what was reported in the MPACT trial. This retrospective analysis suggests that AG is active in PC patients previously treated with either fluoropyrimidine-based therapy or gemcitabine-based therapy with manageable toxicities.

RX 3117: Activity of an oral antimetabolite nucleoside in subjects with pancreatic cancer–Preliminary results of stage II of the phase Ia/IIb study

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Background: RX-3117 is an oral small-molecule antimetabolite, cyclopentyl pyrimidyl nucleoside that is activated by uridine cytidine kinase 2. RX-3117 has shown efficacy in xenograft models of gemcitabine resistant pancreatic, bladder and colorectal cancer. Data from stage 2 of the Phase 1b/2a clinical study of RX3117 as a single agent in subjects with metastatic pancreatic cancer is described below. Methods: Stage 2 of the Phase 1b/2a study (NCT02030067) is designed to evaluate safety, tolerability and efficacy following treatment with 700 mg administered orally once-daily for 5 consecutive days with 2 days off per week for 3 weeks with 1 week off in each 4 week cycle. Eligible subjects (aged ≥ 18 years) had relapsed/refractory metastatic pancreatic cancer. The primary endpoint is a ≥ 20% rate of progression free survival (PFS) benefit (i.e., proportion of subjects with stable disease for at least 4 months) and/or a 10% of evaluable subjects with a partial response rate or better. Results: As of Sep 2017, 44 subjects have been enrolled (22 females, 22 males). The median age was 68 years, ECOG performance statuses were 0 (13 subjects) and 1 (31 subjects) and 6 subjects had received 4 or more prior therapies. One subject had an unconfirmed partial response and 21 subjects met the primary endpoint of stable disease with a duration of 30-224 days. The most frequent adverse events were mild to moderate anemia (19%), mild to moderate fatigue (15%), mild to moderate diarrhea (11%), and severe anemia (9%). Conclusions: This ongoing trial shows an early efficacy signal where RX-3117 is active against advanced pancreatic cancer. The study continues to enroll subjects with advanced pancreatic cancer into stage 2. A phase 2 study with nab-paclitaxel in first-line patients with advanced pancreatic cancer has been started. Clinical trial information: NCT02030067.

Toca 511 and Toca FC in patients with gastrointestinal tumors in the Toca 6 study

TPS880

Background: Toca 511 (vocimagene amiretrorepvec) is an investigational, conditionally lytic, retroviral replicating vector (RRV). RRVs selectively infect cancer cells due to defects in innate and adaptive immune responses found in cancers that support virus replication, and the requirement for cell division for virus integration into the genome. Toca 511 spreads through tumors, stably delivering an optimized cytosine deaminase (CD) gene that converts the prodrug, Toca FC (investigational, extended-release 5-FC) into 5-FU. 5-FU kills infected dividing cancer cells and diffuses and kills surrounding cancer cells, myeloid derived suppressor cells, and tumor associated macrophages, thus reestablishing tumor immunity (Cloughesy et al. Neuro Oncol 2016). In a Phase 1 study, resected high grade glioma tumors expressed CD protein following intravenous (IV) Toca 511.1 In animal models of metastatic colorectal cancer, IV Toca 511 infected metastatic sites, and subsequent 5-FC treatment resulted in decreased tumor size and improved survival (Yagiz et al. Mol Therapy 2015). Methods: Toca 6 is a Phase 1b, multicenter, open-label study (NCT02576665) that aims to investigate changes in immune activity after treatment with Toca 511 & Toca FC in patients with solid tumors, including gastrointestinal tumors. A total of 30 patients who have advanced malignancies, including colorectal and pancreatic cancer, with molecular characteristics that may increase sensitivity to 5-FU or viral infection, or IDH1 mutated solid tumors (e.g., intrahepatic cholangiocarcinoma) will be enrolled. In these patients, Toca 511 is injected IV daily for 3 days, then intratumorally after biopsy. Oral Toca FC is started ~4 weeks later and repeated every 4-6 weeks. Changes from baseline in intratumoral immune activity (infiltrating T-cell subpopulations, B cells, monocytes) at 4 weeks after start of Toca FC are assessed. Contemporaneous peripheral blood is analyzed for effector, memory, Treg, and myeloid lineage cells. Viral RNA, DNA, and CD protein expression in tumor after IV Toca 511 are measured. Safety and efficacy will be determined. Concomitant checkpoint inhibitor therapy may be given following immune activity assessments. The study has enrolled 3 patients. Clinical trial information: NCT02576665.