A phase II study of potentiation of pembrolizumab with binimetinib and bevacizumab in refractory microsatellite stable colorectal cancer

PURPOSE

In this single-institution phase II investigator-initiated study we assessed the ability of MAPK and VEGF pathway blockade to overcome resistance to immunotherapy in microsatellite stable metastatic colorectal cancer (MSS mCRC).

PATIENTS AND METHODS

Patients with MSS, BRAF wild-type mCRC who progressed on ≥2 prior lines of therapy received pembrolizumab, binimetinib, and bevacizumab until disease progression or unacceptable toxicity. After a safety run-in, patients were randomized to a 7-day run-in of binimetinib or simultaneous initiation of all study drugs, to explore whether MEK inhibition may increase tumor immunogenicity. The primary endpoint was objective response rate in all patients combined (ORR, by RECIST v1.1).

RESULTS

Fifty patients received study drug treatment; 54% were male with median age 55 years (range 31-79). The primary endpoint, ORR, was 12.0% (95% confidence interval [CI] 4.5-24.3%), which was not statistically different than the historical control data of 5% (p=0.038, exceeding pre-specified threshold of 0.025). The disease control rate was 70.0% (95% CI 55.4-82.1%), median progression-free survival 5.9 months (95% CI 4.2-8.7 months), and median overall survival 9.3 months (95% CI 6.7-12.2 months). No difference in efficacy was observed between the randomized cohorts. Grade 3 and 4 adverse events were observed in 56% and 8% of patients, respectively; the most common were rash (12%) and increased aspartate aminotransferase (12%).

CONCLUSION

Pembrolizumab, binimetinib, and bevacizumab failed to meet its primary endpoint of higher ORR compared to historical control data, demonstrated a high disease control rate, and demonstrated acceptable tolerability in refractory MSS mCRC.

A Phase Ib Expansion Cohort Evaluating Aurora A Kinase Inhibitor Alisertib and Dual TORC1/2 Inhibitor Sapanisertib in Patients with Advanced Solid Tumors

BACKGROUND

This study further evaluated the safety and efficacy of the combination of alisertib and sapanisertib in an expansion cohort of patients, including a subset of patients with refractory pancreatic adenocarcinoma, with further evaluation of the pharmacodynamic characteristics of combination therapy.

METHODS

Twenty patients with refractory solid tumors and 11 patients with pancreatic adenocarcinoma were treated at the recommended phase 2 dose of alisertib and sapanisertib. Adverse events and disease response were assessed. Patients in the expansion cohort were treated with a 7-day lead-in of either alisertib or sapanisertib prior to combination therapy, with tumor tissue biopsy and serial functional imaging performed for correlative analysis.

RESULTS

Toxicity across treatment groups was overall similar to prior studies. One partial response to treatment was observed in a patient with ER positive breast cancer, and a patient with pancreatic cancer experienced prolonged stable disease. In an additional cohort of pancreatic cancer patients, treatment response was modest. Correlative analysis revealed variability in markers of apoptosis and immune cell infiltrate according to lead-in therapy and response.

CONCLUSIONS

Dual targeting of Aurora A kinase and mTOR resulted in marginal clinical benefit in a population of patients with refractory solid tumors, including pancreatic adenocarcinoma, though individual patients experienced significant response to therapy. Correlatives indicate apoptotic response and tumor immune cell infiltrate may affect clinical outcomes.

First-in-Human Dose-Escalation Study of the Novel Oral Depsipeptide Class I-Targeting HDAC Inhibitor Bocodepsin (OKI-179) in Patients with Advanced Solid Tumors

(1) Background: Histone deacetylases (HDACs) play a critical role in epigenetic signaling in cancer; however, available HDAC inhibitors have limited therapeutic windows and suboptimal pharmacokinetics (PK). This first-in-human phase I dose escalation study evaluated the safety, PK, pharmacodynamics (PDx), and efficacy of the oral Class I-targeting HDAC inhibitor bocodepsin (OKI-179). (2) Patients and Methods: Patients (n = 34) with advanced solid tumors were treated with OKI-179 orally once daily in three schedules: 4 days on 3 days off (4:3), 5 days on 2 days off (5:2), or continuous in 21-day cycles until disease progression or unacceptable toxicity. Single-patient escalation cohorts followed a standard 3 + 3 design. (3) Results: The mean duration of treatment was 81.2 (range 11-447) days. The most frequent adverse events in all patients were nausea (70.6%), fatigue (47.1%), and thrombocytopenia (41.2%). The maximum tolerated dose (MTD) of OKI-179 was 450 mg with 4:3 and 200 mg with continuous dosing. Dose-limiting toxicities included decreased platelet count and nausea. Prolonged disease control was observed, including two patients with platinum-resistant ovarian cancer. Systemic exposure to the active metabolite exceeded the preclinical efficacy threshold at doses lower than the MTD and was temporally associated with increased histone acetylation in circulating T cells. (4) Conclusions: OKI-179 has a manageable safety profile at the recommended phase 2 dose (RP2D) of 300 mg daily on a 4:3 schedule with prophylactic oral antiemetics. OKI-179 is currently being investigated with the MEK inhibitor binimetinib in patients with NRAS-mutated melanoma in the phase 2 Nautilus trial.

Silmitasertib plus gemcitabine and cisplatin first-line therapy in locally advanced/metastatic cholangiocarcinoma: A Phase 1b/2 study

BACKGROUND AND AIMS

This study aimed to investigate safety and efficacy of silmitasertib, an oral small molecule casein kinase 2 inhibitor, plus gemcitabine and cisplatin (G+C) versus G+C in locally advanced/metastatic cholangiocarcinoma.

APPROACH AND RESULTS

This work is a Phase 1b/2 study (S4-13-001). In Phase 2, patients received silmitasertib 1000 mg twice daily for 10 days with G+C on Days 1 and 8 of a 21-day cycle. Primary efficacy endpoint was progression-free survival (PFS) in the modified intent-to-treat population (defined as patients who completed at least one cycle of silmitasertib without dose interruption/reduction) from both phases (silmitasertib/G+C n = 55, G+C n = 29). The response was assessed by Response Evaluation Criteria in Solid Tumors v1.1. The median PFS was 11.2 months (95% confidence interval [CI], 7.6, 14.7) versus 5.8 months (95% CI, 3.1, not evaluable [NE]) ( p  = 0.0496); 10-month PFS was 56.1% (95% CI, 38.8%, 70.2%) versus 22.2% (95% CI, 1.8%, 56.7%); and median overall survival was 17.4 months (95% CI, 13.4, 25.7) versus 14.9 months (95% CI, 9.9, NE) with silmitasertib/G+C versus G+C. Overall response rate was 34.0% versus 30.8%; the disease control rate was 86.0% versus 88.5% with silmitasertib/G+C versus G+C. Almost all silmitasertib/G+C (99%) and G+C (93%) patients reported at least one treatment emergent adverse event (TEAE). The most common TEAEs (all grades) with silmitasertib/G+C versus G+C were diarrhea (70% versus 13%), nausea (59% vs. 30%), fatigue (47% vs. 47%), vomiting (39% vs. 7%), and anemia (39% vs. 30%). Twelve patients (10%) discontinued treatment because of TEAEs during the study.

CONCLUSIONS

Silmitasertib/G+C demonstrated promising preliminary evidence of efficacy for the first-line treatment of patients with locally advanced/metastatic cholangiocarcinoma.

Impact of early-onset colorectal cancer on utilization of chemotherapy and outcomes in patients with stage II disease

85

Background: Rising rates of early-onset colorectal cancer (EOCRC) pose a dilemma for clinicians when deciding how to treat early-stage patients to maximize outcomes. While standard-of-care for Stage II colon cancer is largely surgical resection, evidence suggests that treatment selection may differ by patient age. We sought to determine whether rates of adjuvant chemotherapy administration differ between early and later-onset patients with Stage II CRC. Methods: Data were derived from the Flatiron National Database spanning 1/1/2003 to 8/1/2021. Patients 18 years or older with Stage II CRC were grouped into those aged 18-49 (EOCRC) and those aged 50 or older (LOCRC). Demographic characteristics, ECOG score, stage and site of tumor, and chemotherapy were included for all patients. Primary outcomes of interest included rates of adjuvant chemotherapy administration by age and ethnicity. Univariate and multivariable logistic regression models were used to evaluate relationships between chemotherapy administration, age groups, and ethnicity while adjusting for significant covariates. Results: Of 2133 patients with Stage II CRC, 1606 patients with complete data were included. A secondary analysis of 1065 patients with colon cancer was performed to address potential confounding factors related to neoadjuvant and/or adjuvant chemotherapy given in patients with stage II rectal cancer. Mean age of EOCRC patients was 45.0 years (range: 41.0-48.0) vs. 68.0 years (60.0-75.0) for LOCRC. Adjusting for ethnicity, gender, site, and ECOG score, multivariate analysis showed EOCRC patients received chemotherapy significantly more often than LOCRC patients for stage II CRC (adjusted odds ratio 1.85, 95% CI 1.32-2.60, p < 0.001). Similar findings were observed in the colon cancer only cohort (adjusted OR 2.02, 95% CI 1.31-3.09, p < 0.001). By ethnicity, non-Hispanic patients received chemotherapy at significantly lower rates than Hispanic patients in both cohorts (adjusted odds ratio 0.58, 95% CI 0.39-0.88, p = 0.009 and adjusted odds ratio 0.55, 95% CI 0.34-0.91, p = 0.018). In a subgroup analysis of Stage IIA patients, multivariate logistic regression adjusting for gender, ECOG, site, and ethnicity showed that patients with EOCRC were more likely to receive chemotherapy than patients with LOCRC (adjusted odds ratio 1.91, 95% CI 1.21-2.99, p = 0.005). Updated survival data will be presented. Conclusions: Adjuvant chemotherapy is given preferentially in Stage II EOCRC, even in Stage IIA disease, despite deviation from established guidelines. This may expose patients at low risk for recurrence to unnecessary toxicities and reveals potential provider bias in favor of younger patients in aggressively treating CRC, despite unclear evidence for any outcome benefit.

Trial in progress: A phase II study (with safety run-in) of evorpacept (ALX148), cetuximab, and pembrolizumab in patients with refractory microsatellite-stable metastatic colorectal cancer (AGICC-ALX148 21CRC01)

TPS257

Background: Refractory microsatellite stable colorectal cancer (MSS CRC) is immunologically cold and single-agent anti-PD-1/PD-L1 drugs are ineffective; novel immune-based approaches are needed. Evorpacept (E, ALX148) is an engineered protein (high-affinity CD47-blocker fused to an inactive IgG Fc region), which blocks the CD47/SIRPα innate immune inhibitory phagocytosis checkpoint expressed on CRC and phagocytes, respectively. The Fc region of E does not bind to Fcγ receptors, thereby limiting hematologic toxicity, and is intended to be given in combination. In CT26 CRC syngeneic models, E ± anti-PD-1 monoclonal antibody decreases tumor growth, reduces myeloid immunosuppression, increases dendritic cell activation, and increases T cell activation (Kauder, 2018); E enhances the antibody-dependent cellular phagocytosis activity of cetuximab (C) in vitro (Kauder, 2018); and E + pembrolizumab (P) was well-tolerated in the first-in-human trial (Lakhani, 2021). Methods: AGICC-ALX148 21CRC01 (NCT05167409) is a phase 2, single-arm, multicenter, investigator-initiated trial of E (15 mg/kg weekly), C (400 mg/m2 then 250 mg/m2 weekly), and P (200 mg every 3 weeks) in 21-day cycles for patients with unresectable MSS/proficient mismatch repair CRC refractory to oxaliplatin, irinotecan, and a fluoropyrimidine, regardless of tumor sidedness and RAS/BRAF status. Additional key eligibility criteria include ECOG performance status 0-1, evaluable disease per RECIST v1.1, adequate hematologic and end organ function, absence of prior checkpoint inhibitor use, and absence of significant autoimmune disease. Six patients will be enrolled in Stage 1 (safety run-in) and treated with ECP. The study will proceed to Stage 2 (dose expansion, N = 42, and all treated with ECP) if less than 33% of patients in Stage 1 experience a dose-limiting toxicity. Otherwise, additional patients will be enrolled in Stage 1 at lower dose level(s). The co-primary objectives are to determine 1) the recommended dose of E with CP, and 2) objective response rate by RECIST v1.1 (by one-sided exact test with α = 0.05, H0 p ≤ 3% [historical controls], HA p ≥ 15%; power is 87%). The study will close for futility if there are no responses (partial or complete) in the first 24 evaluable patients (by MinMax design with α = 0.025 [1-sided]; power is 87%). Secondary and exploratory aims include determination of progression-free survival, overall survival, safety, response assessment by iRECIST, and blood- and tumor-based immune modulation and baseline tumor expression (PD-L1, EGFR, and CD47) for association with tumor response. The study is open through the Academic GI Cancer Consortium and 5 patients have been enrolled at time of submission. Clinical trial information: NCT05167409 .

Current Practice in Carcinoid Heart Disease and Burgeoning Opportunities

OPINION STATEMENT

Cardiac surgery with tricuspid valve and potentially pulmonic valve replacement at an experienced center is currently the most effective strategy available for the treatment of carcinoid heart disease. Cardiac surgery for carcinoid heart disease requires a multidisciplinary team including cardiology, medical oncology, cardiothoracic anesthesia, and cardiac surgery. Without cardiac surgery, morbidity and mortality from carcinoid heart disease is high. Aggressive management of carcinoid before and after cardiac surgery is critical. Over time, though, circulating carcinoid hormones can lead to destruction of prosthetic valves as well, resulting in recurrent right heart failure. Percutaneous options for valve repair may be on the horizon for management of carcinoid heart disease.

ATM kinase inhibitor AZD0156 in combination with irinotecan and 5-fluorouracil in preclinical models of colorectal cancer

Background

AZD0156 is an oral inhibitor of ATM, a serine threonine kinase that plays a key role in DNA damage response (DDR) associated with double-strand breaks. Topoisomerase-I inhibitor irinotecan is used clinically to treat colorectal cancer (CRC), often in combination with 5-fluorouracil (5FU). AZD0156 in combination with irinotecan and 5FU was evaluated in preclinical models of CRC to determine whether low doses of AZD0156 enhance the cytotoxicity of irinotecan in chemotherapy regimens used in the clinic.

Methods

Anti-proliferative effects of single-agent AZD0156, the active metabolite of irinotecan (SN38), and combination therapy were evaluated in 12 CRC cell lines. Additional assessment with clonogenic assay, cell cycle analysis, and immunoblotting were performed in 4 selected cell lines. Four colorectal cancer patient derived xenograft (PDX) models were treated with AZD0156, irinotecan, or 5FU alone and in combination for assessment of tumor growth inhibition (TGI). Immunofluorescence was performed on tumor tissues. The DDR mutation profile was compared across in vitro and in vivo models.

Results

Enhanced effects on cellular proliferation and regrowth were observed with the combination of AZD0156 and SN38 in select models. In cell cycle analysis of these models, increased G2/M arrest was observed with combination treatment over either single agent. Immunoblotting results suggest an increase in DDR associated with irinotecan therapy, with a reduced effect noted when combined with AZD0156, which is more pronounced in some models. Increased TGI was observed with the combination of AZD0156 and irinotecan as compared to single-agent therapy in some PDX models. The DDR mutation profile was variable across models.

Conclusions

AZD0156 and irinotecan provide a rational and active combination in preclinical colorectal cancer models. Variability across in vivo and in vitro results may be related to the variable DDR mutation profiles of the models evaluated. Further understanding of the implications of individual DDR mutation profiles may help better identify patients more likely to benefit from treatment with the combination of AZD0156 and irinotecan in the clinical setting.

A phase Ib study of the combination of alisertib (Aurora A kinase inhibitor) and MLN0128 (dual TORC1/2 Inhibitor) in patients with advanced solid tumors, final expansion cohort data

3112

Background: In prior work, senescence and up-regulation of genes in the PI3K/AKT/mTor pathway were observed in patient-derived xenograft models treated with alisertib to resistance, and tumor growth inhibition was observed when MLN0128 (sapanisertib) was added to alisertib. In a previously reported dose escalation cohort of patients with advanced solid tumors treated with the combination of alisertib and MLN0128, the maximum tolerated dose (MTD) was alisertib 30mg BID days 1-7 of a 21-day cycle and MLN0128 2mg daily on a continuous schedule. Presented here are final results from the dose expansion portion of this clinical trial. Methods: Three cohorts of patients were treated with the combination at the MTD. Patients with advanced solid tumors, refractory to standard therapy, were assigned to either single-agent treatment with alisertib (Group 1) or MLN0128 (Group 2) on days 1-7 of Cycle 1. For the remainder of the study, patients received combination treatment. Group 3 enrolled patients with refractory pancreatic adenocarcinoma who were treated with standard dosing of the combination. Biopsies were performed in Groups 1 and 2 prior to treatment initiation and after both the single-agent lead-in and 7 days of combination treatment, with assessment of pharmacodynamic markers. Functional imaging was performed pre-treatment and after Cycle 1. Results: A total of 31 patients with refractory cancers were treated. Group 1 included patients with breast (5), colorectal (2), ovarian (2), and pancreatic (1) cancers. Group 2 included patients with breast (4), colorectal (2), pancreatic (2), uterine (1), and kidney (1) cancers. Eleven patients with refractory pancreatic cancer were treated in Group 3. Median time on study was 11.6 weeks in Group 1, 6 weeks in Group 2, and 9 weeks in Group 3. One partial response was documented in Group 1. One patient with pancreatic cancer in Group 1 continued on study for 47 weeks, and another pancreatic cancer patient in Group 3 continued on study for 28 weeks. Toxicity was similar across cohorts, with mucositis, fatigue, hyperglycemia and neutropenia reported as most common. Biopsy results were significant for increased apoptosis and tumor-infiltrating immune cells noted in tissues from 4 patients treated with the MLN0128 lead-in. Decreased F18-FDG uptake on PET/CT, often with increased ADC values in diffusion MRI, was observed in metastatic liver lesions in 4 patients after Cycle 1. Conclusions: In an expansion cohort of 31 patients treated with the combination of MLN0128 and alisertib at the previously defined MTD, treatment was tolerable with an expected toxicity profile. Prolonged stable disease was observed in 2 patients with pancreatic cancer. Increased apoptosis and tumor-infiltrating immune cells were noted in tissues from patients treated with a lead-in of MLN0128. Clinical trial information: NCT02719691.

A phase II study of pembrolizumab, binimetinib, and bevacizumab in patients with microsatellite-stable, refractory, metastatic colorectal cancer (mCRC)

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Background: To date, immune-checkpoint inhibition for microsatellite stable (MSS) mCRC has been ineffective, though targeted therapy combination strategies may be promising. This phase II, investigator-initiated trial (NCT03475004) was designed to evaluate the efficacy and safety of the three-drug combination of pembrolizumab (pembro), binimetinib, and bevacizumab in patients with advanced, MSS treatment-refractory colorectal cancer. Methods: Patients with mCRC locally determined to be MSS and whom have progressed on two prior lines of therapy were enrolled. Treatment consists of pembro (200 mg every 3 weeks), binimetinib (45 mg BID) and bevacizumab (7.5 mg/kg every 3 weeks) until disease progression or unacceptable toxicity. The primary endpoint is PFS using RECIST v1.1 by investigator review. Additional endpoints include objective response rate, disease control rate at time of first re-staging (2 mo), duration of response, and safety and tolerability. Results: 50 patients have been enrolled (accrual is completed). 53% of patients are male and the mean age is 53.6 (range 31-79). The mean number of prior therapies is 5.3. At the time of preliminary data review, 39 patients are evaluable for response data. The median PFS was 5.8 mo (95% CI 4.2 to 8.9). The objective response rate was 13% with 5 partial responses. 24 patients (62%) had stable disease and 10 (26%) had progressive disease as the best response. The disease control rate at the time of first re-staging was 74%. Median duration of response was 6.5 mo. 19 (40%) patients experienced serious adverse events; the most common grade ≥3 adverse events included transaminase elevation (15%), diarrhea (11%), acneiform rash (9%), hypertension (9%), and anemia (9%). Conclusions: Preliminary results from this phase II study indicate that this regimen of pembrolizumab, binimetinib, and bevacizumab has promising activity and acceptable tolerability in this heavily pre-treated population of patients with MSS metastatic colorectal cancer. Final results will be presented as well as ongoing correlative studies. Clinical trial information: NCT03475004.

Multicenter randomized phase II trial of atezolizumab with or without cobimetinib in biliary tract cancers

BACKGROUNDMEK inhibitors have limited activity in biliary tract cancers (BTCs) as monotherapy but are hypothesized to enhance responses to programmed death ligand 1 (PD-L1) inhibition.METHODSThis open-label phase II study randomized patients with BTC to atezolizumab (anti-PD-L1) as monotherapy or in combination with cobimetinib (MEK inhibitor). Eligible patients had unresectable BTC with 1 to 2 lines of prior therapy in the metastatic setting, measurable disease, and Eastern Cooperative Oncology Group (ECOG) performance status less than or equal to 1. The primary endpoint was progression-free survival (PFS).RESULTSSeventy-seven patients were randomized and received study therapy. The trial met its primary endpoint, with a median PFS of 3.65 months in the combination arm versus 1.87 months in the monotherapy arm (HR 0.58, 90% CI 0.35-0.93, 1-tail P = 0.027). One patient in the combination arm (3.3%) and 1 patient in the monotherapy arm (2.8%) had a partial response. Combination therapy was associated with more rash, gastrointestinal events, CPK elevations, and thrombocytopenia. Exploratory analysis of tumor biopsies revealed enhanced expression of antigen processing and presentation genes and an increase in CD8/FoxP3 ratios with combination treatment. Patients with higher baseline or lower fold changes in expression of certain inhibitory ligands (LAG3, BTLA, VISTA) on circulating T cells had evidence of greater clinical benefit from the combination.CONCLUSIONThe combination of atezolizumab plus cobimetinib prolonged PFS as compared with atezolizumab monotherapy, but the low response rate in both arms highlights the immune-resistant nature of BTCs.TRIAL REGISTRATIONClinicalTrials.gov NCT03201458.FUNDINGNational Cancer Institute (NCI) Experimental Therapeutics Clinical Trials Network (ETCTN); F. Hoffmann-La Roche, Ltd.; NCI, NIH (R01 CA228414-01 and UM1CA186691); NCI's Specialized Program of Research Excellence (SPORE) in Gastrointestinal Cancers (P50 CA062924); NIH Center Core Grant (P30 CA006973); and the Passano Foundation.

Outcome of neoadjuvant treatment for pancreatic cancer in elderly patients: comparative, observational cohort study

BACKGROUND

Use of neoadjuvant therapy for elderly patients with pancreatic cancer has been debatable. With FOLFIRINOX (folinic acid, 5-fluorouracil, irinotecan, oxaliplatin) or gemcitabine plus nab-paclitaxel (GnP) showing tremendous effects in improving the overall survival of patients with borderline resectable and locally advanced pancreatic cancer, there is no definitive consensus regarding the use of this regimen in the elderly.

METHODS

This study evaluated the eligibility of elderly patients with borderline resectable or locally advanced pancreatic cancer for neoadjuvant therapy. Patients registered in the database of pancreatic cancer at the University of Colorado Cancer Center, who underwent neoadjuvant treatment between January 2011 and March 2019, were separated into three age groups (less than 70, 70-74, 75 or more years) and respective treatment outcomes were compared.

RESULTS

The study included 246 patients with pancreatic cancer who underwent neoadjuvant treatment, of whom 154 and 71 received chemotherapy with FOLFIRINOX and GnP respectively. Among these 225 patients, 155 were younger than 70 years, 36 were aged 70-74 years, and 34 were aged 75 years or older. Patients under 70 years old received FOLFIRINOX most frequently (124 of 155 versus 18 of 36 aged 70-74 years, and 12 of 34 aged 75 years or more; P < 0.001). Resectability was similar among the three groups (60.0, 58.3, and 55.9 per cent respectively; P = 0.919). Trends towards shorter survival were observed in the elderly (median overall survival time 23.6, 18.0, and 17.6 months for patients aged less than 70, 70-74, and 75 or more years respectively; P = 0.090). After adjusting for co-variables, age was not a significant predictive factor.

CONCLUSION

The safety and efficacy of multiagent chemotherapy in patients aged 75 years or over were similar to those in younger patients. Modern multiagent regimens could be a safe and viable treatment option for clinically fit patients aged at least 75 years.

Tissue tumor mutational burden (TMB) as a biomarker of efficacy with immune checkpoint inhibitors (ICI) in metastatic gastrointestinal (mGI) cancers

e14559

Background: While TMB is very dependent on methodology, tissue TMB-H (≥10 mutations/megabase) may predict benefit with ICIs. Pembrolizumab received tissue-agnostic approval for TMB-H unresectable cancers in 2020, but little is known about TMB as a predictive biomarker in mGI cancers. We hypothesized that tissue TMB will correlate with efficacy of ICIs in mGI cancers. Methods: A retrospective chart review identified patients with mGI cancers who received an anti-PD-(L)1 drug and had known TMB at a single academic center from 2012 to 2020. The association of TMB with objective response rate (ORR), progression-free survival (PFS), and overall survival (OS) was analyzed using the Fisher’s exact and Log-rank tests. Survival curves were generated using the Kaplan-Meier method. Cox proportional hazard and logistic regression models were used to adjust for microsatellite status. Significance was prespecified at 0.05. Results: 83 patients were identified and included. The most common cancer types were colorectal adenocarcinoma (AC, n = 29), esophageal/gastric AC (n = 21) and SCC (n = 4), cholangiocarcinoma (n = 11), anal SCC (n = 7), and pancreas AC (n = 7). Average age was 61, average number of lines of prior systemic therapy for advanced disease was 1.3 (range 0-4), and 37% of patients were treated on a clinical study. All patients received an anti-PD-(L)1 drug; 6%, 2%, and 36% also received ipilimumab, cytotoxic chemotherapy, and other combinations, respectively. Among those with esophageal/gastric cancer, 76% had known PD-L1 CPS (84% ≥1, 63% ≥5, 42% ≥10). TMB was primarily determined by Foundation One CDx (87%). TMB ranged from 0 to 54; n = 22 (27%) were TMB-H (of these, n = 10 were microsatellite instability-high (MSI-H)), and n = 61 were TMB-L ( < 10 mutations/megabase; of these, n = 2 were MSI-H). The prevalence of TMB-H and microsatellite stable (MSS) was 14.4%. TMB-L, compared to TMB-H, was associated with inferior ORR (3.5% vs 55.6%; odds ratio (OR) 0.045; p < 0.001) and PFS (median 12.7 vs 29.3 weeks; hazard ratio (HR) 2.70; p = 0.001), but not OS (HR 1.20; p = 0.60). In patients with MSS disease, TMB-L, compared to TMB-H, was associated with inferior ORR (OR 0.13; p = 0.04) but not PFS (HR 1.76; p = 0.07) or OS (HR 0.89; p = 0.79). In subgroup analyses, ORR was not significantly associated to tumor type in all or MSS patients. TMB as a continuous variable, in patients with MSS disease, was positively correlated with ORR (p = 0.02) and PFS (p = 0.04), but not OS (p = 0.59). Among all patients, PFS and OS data is immature (median follow-up 13 and 31 weeks). Conclusions: In a single center retrospective study of patients with mGI cancers treated with ICIs, TMB-H was associated with improved ORR and PFS compared to TMB-L. In patients with MSS disease, ORR remained significant. PFS and OS data are immature. TMB as a biomarker of efficacy with ICIs in mGI cancers warrants further study to guide clinical use.

Utility of chemotherapy given before and/or after cytoreductive surgery and hyperthermic intraperitoneal chemotherapy for appendiceal adenocarcinoma with peritoneal metastases

e16276

Background: Appendiceal adenocarcinoma is relatively rare and often diagnosed incidentally during operations for acute appendicitis. It is commonly associated, either at time of initial presentation or upon recurrence, with peritoneal metastases. A typical treatment strategy for patients with peritoneal disease includes cytoreductive surgery (CRS) with hyperthermic intraperitoneal chemotherapy (HIPEC). Extrapolating largely from literature in colorectal cancer, chemotherapy is frequently given before and/or after CRS/HIPEC though high-level evidence to support this is lacking. We sought to evaluate the effect of systemic chemotherapy on survival. Methods: Utilizing a database of CRS/HIPEC procedures at University of Colorado Hospital from 2008 to present we retrospectively reviewed cases of appendiceal adenocarcinoma. Data collected included staging, histologic grade, chemotherapy given, surgical outcomes, and time to disease recurrence. Patients without adequate information regarding treatment, or without at least 1 year of clinical follow-up, were excluded. Associations between administration of chemotherapy or histologic grade and 1-year DFS were analyzed using Fisher’s exact test, and logistic regression was used to assess whether 1-year DFS were different in chemotherapy-treated patients when adjusted for histologic grade. Results: In total, 117 cases reviewed indicated an appendiceal pathology. Of these, 54 cases in a total of 51 patients met the specified criteria for pathology and completeness and length of follow-up information. The average age was 58 years (range 26-81 years). Adenocarcinoma was graded as low in 15 (28%) cases, intermediate in 18 (33%) cases, and high in 21 (39%) cases. 23 (43%) patients received no chemotherapy while 31 (57%) received chemotherapy before and/or after surgery. In the overall population, there was no significant effect of chemotherapy on survival, with 1-year DFS demonstrated in 74.2% of patients receiving some chemotherapy and 70% in patients not receiving chemotherapy (p = 0.765). One-year DFS was achieved in 86% of low-grade cases, 61% of intermediate-grade cases, and 71% of high-grade cases, though this was also not statistically significant (p = 0.254). Furthermore, when 1-year DFS between chemotherapy and non-chemotherapy patients was adjusted for grade, there was again no significant interaction (odds ratio = 0.48, 95% C.I. (0.13-1.64), p = 0.763). Conclusions: In this small, single-institution experience of patients with peritoneal appendiceal adenocarcinoma, there was no significant effect of chemotherapy administration on 1-year DFS. These findings are likely affected by significant confounding with the small sample size and retrospective nature of the data. Further investigation on a larger scale is warranted.

Phase 1 study of OKI-179, an oral class 1-selective depsipeptide HDAC inhibitor, in patients with advanced solid tumors: Final results

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Background: OKI-179 is a novel, oral pro-drug analog of largazole, a compound in the romidepsin-depsipeptide class of natural products. OKI-006, the active metabolite of OKI-179, inhibits HDAC 1,2,3 (IC50 = 1.2, 2.4, 2.0 nM, respectively), with no significant inhibition of Class IIa HDACs and has shown promising activity in preclinical models of solid tumors. We conducted a first-in-human dose escalation study of OKI-179 in patients with advanced solid tumors. Methods: Patients with advanced solid tumors, ECOG ≤1, normal QTc, and disease refractory to or with no available standard therapy options were treated with OKI-179 with either intermittent dosing (once daily for 4 days on 3 days off) or continuous dosing (once daily). Dose escalation was conducted using a standard 3+3 design. Pharmacokinetic (PK) and pharmacodynamic (PD) testing was performed at various time points after dosing. Results: As of Feb 4, 2021, 26 patients (19 female, 7 male) were enrolled with mean age of 63 (range 41-83). Patients received a median of 5 (range 1-11) prior lines of therapy and most common tumor types included pancreatic (N = 5), breast (N = 4), lung (N = 4), and ovarian cancer (N = 4). Twenty patients were treated in intermittent dosing cohorts from 30-450 mg. One DLT (Grade 2 [G2] thrombocytopenia) occurred in the 450 mg cohort which was expanded to 6 patients without subsequent DLTs. Six patients were treated in 2 continuous dosing cohorts of 200 mg and 300 mg. Two of 3 patients in the 300 mg cohort had DLTs of G3-4 thrombocytopenia and no DLTs were observed in 3 patients treated at 200 mg PO daily. The most common adverse events (AEs) were nausea (62%), fatigue (42%), anemia (39%), anorexia (27%), and vomiting (23%). These AE’s were G1-2 except for G3 anemia (12%), G3 fatigue (12%), and G3 anorexia (4%). No other G4-5 treatment-related AEs occurred. Median time on study was 79 days and best response was stable disease (SD) in 10 of 24 patients evaluable for efficacy (42%). Prolonged SD was observed in patients with platinum-resistant serous ovarian cancer (446 days) and adenoid cystic nasopharyngeal carcinoma (256 days). OKI-006 achieved consistent exposure with Cmax > 2,000 ng/ml and AUC > 8,000 hr*ng/ml, well above the targeted exposure for efficacy based on pre-clinical studies in murine models. Tmax was 2 hours and T1/2 was 6-8 hours. OKI-179 treatment resulted in > 3X increased T cell histone H3K9 and H3K27 acetylation within circulating PBMCs at doses of 180 - 450 mg. Conclusions: OKI-179 has a manageable safety profile, with thrombocytopenia being the on-target DLT. It has a favorable PK profile and demonstrated on-target PD effects at tolerable doses. The MTD and RP2D for OKI-179 was 450 mg daily for intermittent dosing and 200 mg daily for continuous dosing. Phase 2 studies are being designed, with a focus on combination with endocrine therapy in ER+ breast cancer and in NRAS-mutant melanoma. Clinical trial information: NCT03931681.

WEE1 Inhibition in Combination With Targeted Agents and Standard Chemotherapy in Preclinical Models of Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal cancer with high incidences of p53 mutations. AZD1775 (adavosertib, previously MK-1775) is a small molecule WEE1 inhibitor that abrogates the G2M checkpoint and can potentially synergize with DNA damaging therapies commonly used in PDAC treatment. The purpose of this study was to identify combination partners for AZD1775, including standard chemotherapy or targeted agents, in PDAC preclinical models. Low powered preliminary screens demonstrated that two of the four PDX models responded better to the combinations of AZD1775 with irinotecan or capecitabine than to either single agent. Following the screens, two full powered PDAC PDX models of differing p53 status were tested with the combinations of AZD1775 and irinotecan or capecitabine. The combinations of AZD1775 and SN38 or 5-FU were also tested on PDAC cell lines. Cellular proliferation was measured using an IncuCyte Live Cell Imager and apoptosis was measured using a Caspase-Glo 3/7 assay. Flow cytometry was conducted to measure alterations in cell cycle distribution. Western blot analysis was used to determine the effects of the drug combinations on downstream effectors. In PDX models with mutated p53 status, there was significant tumor growth inhibition from the combination of AZD1775 with irinotecan or capecitabine (P ≤ 0.03), while PDX models with wild type p53 did not show anti-tumor synergy from the same combinations (P ≥ 0.08). The combination of AZD1775 with SN38 or 5-FU significantly decreased proliferation in all PDAC cell lines, and enhanced apoptosis in multiple cell lines. Cell cycle distribution was disrupted from the combination of AZD1775 with SN38 or 5-FU which was recorded as G2M arrest and decreased G1 phase. AZD1775 inhibited phospho-CDC2 and increased the expression of γH2AX that was either maintained or enhanced after combination with SN38 or 5-FU. The combination of AZD1775 with irinotecan/SN38 or capecitabine/5-FU showed anti-tumor effects in vivo and in vitro in PDAC models. These results support further investigation for these combination strategies to enhance outcomes for PDAC patients.

Impact of Radiation Dose on Postoperative Complications in Esophageal and Gastroesophageal Junction Cancers

Introduction: The impact of radiation prescription dose on postoperative complications during standard of care trimodality therapy for operable stage II-III esophageal and gastroesophageal junction cancers has not been established. Methods: We retrospectively reviewed 82 patients with esophageal or gastroesophageal junction cancers treated between 2004 and 2016 with neoadjuvant chemoradiation followed by resection at a single institution. Post-operative complications within 30 days were reviewed and scored using the Comprehensive Complication Index (CCI). Results were compared between patients treated with <50 Gy and ≥ 50 Gy, as well as to published CROSS study neoadjuvant chemoradiation group data (41.4 Gy). Results: Twenty-nine patients were treated with <50 Gy (range 39.6-46.8 Gy) and 53 patients were treated with ≥ 50 Gy (range 50.0-52.5 Gy) delivered using IMRT/VMAT (41%), 3D-CRT (46%), or tomotherapy IMRT (12%). Complication rates and CCI scores between our <50 Gy and ≥ 50 Gy groups were not significantly different. Assuming a normal distribution of the CROSS data, there was no significant difference in CCI scores between the CROSS study neoadjuvant chemoradiation, <50 Gy, or ≥ 50 Gy groups. Rates of pulmonary complications were greater in the CROSS group (50%) than our <50 Gy (38%) or ≥ 50 Gy (30%) groups. Conclusions: In selected esophageal and gastroesophageal junction cancer patients, radiation doses ≥ 50 Gy do not appear to increase 30 day post-operative complication rates. These findings suggest that the use of definitive doses of radiotherapy (50-50.4 Gy) in the neoadjuvant setting may not increase post-operative complications.

Silmitasertib (CX-4945) in combination with gemcitabine and cisplatin as first-line treatment for patients with locally advanced or metastatic cholangiocarcinoma: A phase Ib/II study

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Background: Silmitasertib (CX-4945), an oral small molecule inhibitor of casein kinase 2 (CK2), has exhibited preclinical antitumor activity and strong synergism with gemcitabine + cisplatin. We investigated the safety and efficacy of silmitasertib in combination with gemcitabine + cisplatin in patients with unresectable cholangiocarcinoma (CCA). Methods: S4-13-001 is a multicenter, open-label, phase Ib/II study of silmitasertib in combination with gemcitabine + cisplatin in patients with locally advanced or metastatic CCA. The phase Ib portion included dose-escalation, expansion, and exploratory cohorts of silmitasertib with doses ranging from 200 to 1000 mg bid (6 days for the escalation/expansion cohorts and 10 and 21 days’ continuous dosing for the exploratory cohorts). In the phase II portion patients received silmitasertib 1000 mg bid for 10 days in combination with gemcitabine + cisplatin on days 1 & 8 over a 21-day cycle. In this interim analysis, we present findings from the combined population of patients from the phase Ib and II portions of the study. Response to treatment was assessed by RECIST v1.1 every 6 weeks. Primary efficacy outcome measure was progression-free survival (PFS). ClinicalTrials.gov (NCT02128282). Results: A total of 87 patients were enrolled and received silmitasertib in the phase Ib (n=50) and phase II (n=37) portions of the study. Of these, 55 patients were evaluable for efficacy with details as follows: median PFS 11.1 (95% CI 7.6–14.7) months; median overall survival (OS) 17.4 (95% CI 13.4–25.7) months; overall response rate (ORR) 32.1%; and disease control rate (DCR) 79.3%. Almost all patients (79/87; 90.8%) evaluable for safety reported ≥1 treatment-related adverse event (TEAE). The most common TEAEs (all grades) with silmitasertib were diarrhea (65.5%), nausea (50.6%), vomiting (33.3%), fatigue (31.0%), and anemia (21.8%). The most common grade ≥3 TEAEs were diarrhea (13.8%), neutropenia (11.5%), nausea (9.2%), anemia (8.0%), and thrombocytopenia (8.0%). Eleven patients (12.6%) discontinued treatment due to TEAEs. Conclusions: Silmitasertib in combination with gemcitabine + cisplatin yields promising preliminary evidence of efficacy in patients with locally advanced or metastatic CCA. Based on these data a randomized phase III trial is planned. Clinical trial information: NCT02128282.

A single-institution experience using total neoadjuvant therapy to treat locally advanced rectal cancer

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Background: The management of locally advanced rectal cancer has historically included preoperative chemoradiation followed by surgery and then adjuvant chemotherapy. Recently there has been an increasing utilization of preoperative chemotherapy in addition to standard chemoradiation, a strategy known as total neoadjuvant therapy (TNT). TNT has been offered to patients at the University of Colorado Cancer Center since 2015. Methods: Records of all patients presenting to the University of Colorado colorectal multidisciplinary clinic since 2015 were screened for treatment with TNT. Data collected on these patients included demographic information, diagnosis and initial staging, preoperative treatment received, and surgical outcomes including treatment response and pathological stage. TNT included preoperative chemotherapy with oxaliplatin combined with either 5-FU (FOLFOX) or capecitabine (CAPOX) as well as chemoradiation, generally given with concurrent capecitabine. Patients then underwent surgical resection; if a complete clinical response was achieved with TNT, non-operative management (NOM) was offered. Results: A total of 81 patients thus far have undergone TNT followed by resection or, if complete clinical response and preferred by the patient, NOM. The mean age of patients was 56 years, ranging from 23 to 87, and 60% of patients were male. The majority of patients (67) had stage III disease at presentation while 1 had stage 1 (T2N0) disease, 11 had stage II disease and 2 patients had oligometastatic disease. Ultimately 13 patients (16%) opted for non-operative management after being found to have a complete clinical response following TNT. Of the 68 patients who underwent surgical resection, 21 (31%) had a pathological complete response, with another 14 (21%) with near-complete response. 28 patients (41%) had a partial treatment response and 5 (7%) had no treatment response. In total, the rate of complete clinical or pathologic response was 42%. Treatment was overall well-tolerated with 90% of patients receiving the full planned dose of radiation and 98% of patients completing all planned cycles of chemotherapy, though most of them with typical dose reductions needed. Of the patients who underwent surgery, 49 (72%) had low anterior resection and 19 (28%) had an abdominoperineal resection. Of patients with temporary ileostomies, 85% of them had their ileostomy reversed within 10 weeks of surgery. Conclusions: Treatment of locally advanced rectal cancer by a total neoadjuvant approach is well-tolerated and results in a high rate of clinical and pathological complete response.

Preclinical and Dose-Finding Phase I Trial Results of Combined Treatment with a TORC1/2 Inhibitor (TAK-228) and Aurora A Kinase Inhibitor (Alisertib) in Solid Tumors

PURPOSE

The purpose of this study was to evaluate the rational combination of TORC1/2 inhibitor TAK-228 and Aurora A kinase inhibitor alisertib in preclinical models of triple-negative breast cancer (TNBC) and to conduct a phase I dose escalation trial in patients with advanced solid tumors.

EXPERIMENTAL DESIGN

TNBC cell lines and patient-derived xenograft (PDX) models were treated with alisertib, TAK-228, or the combination and evaluated for changes in proliferation, cell cycle, mTOR pathway modulation, and terminal cellular fate, including apoptosis and senescence. A phase I clinical trial was conducted in patients with advanced solid tumors treated with escalating doses of alisertib and TAK-228 using a 3+3 design to determine the maximum tolerated dose (MTD).

RESULTS

The combination of TAK-228 and alisertib resulted in decreased proliferation and cell-cycle arrest in TNBC cell lines. Treatment of TNBC PDX models resulted in significant tumor growth inhibition and increased apoptosis with the combination. In the phase I dose escalation study, 18 patients with refractory solid tumors were enrolled. The MTD was alisertib 30 mg b.i.d. days 1 to 7 of a 21-day cycle and TAK-228 2 mg daily, continuous dosing. The most common treatment-related adverse events were neutropenia, fatigue, nausea, rash, mucositis, and alopecia.

CONCLUSIONS

The addition of TAK-228 to alisertib potentiates the antitumor activity of alisertib in vivo, resulting in increased cell death and apoptosis. The combination is tolerable in patients with advanced solid tumors and should be evaluated further in expansion cohorts with additional pharmacodynamic assessment.

Abstract 6387: Therapeutic targeting of lipid oxidation and apoptosis in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is currently the fourth leading cause of cancer deaths with more than 56,000 new cases estimated to be diagnosed in 2019. Current treatment options for PDAC include radiation and chemotherapeutic regimens, however these targeted therapies are ineffective for patients with advanced disease progression. Additionally, the dense stromal nature of PDAC tumors create challenges to target the cancer cells resulting in incomplete cell killing and eventual drug resistance. Recent evidence has shown that CPT1A, an enzyme that regulates the entry of lipids into mitochondria for β-oxidation, is strongly expressed in several cancers. CPT1A is located on the mitochondrial membrane and potentially interacts with BCL-2, an anti-apoptotic protein that promotes tumor maintenance and metastasis. Metabolic stress can activate the anti-apoptotic effects of BCL-2, reprograming metabolism to use fat oxidation for cancer survival. Therefore, a co-inhibition using the selective BCL-2 inhibitor, venetoclax, with agents that inhibit CPT1A and β-oxidation, could be a novel strategy for PDAC. There are few studies considering CPT1A as a therapeutic target for PDAC. Current available drugs to target these pathways include the anti-anginal ranolazine, and CPT1A inhibitors etomoxir and perhexiline. Previous studies have shown that expression of BCL-2 by tumor cells is necessary for BCL-2 inhibitors to be effective. We initially wanted to determine the expression of BCL-2 and CPT1A in PDAC cells utilizing western blot and rtPCR, and to confirm their proximity using a proximity ligation assay (PLA). PDAC cells were then plated in 96 well plates and Cell Titer-Glo assays were performed to determine effective concentrations of single agent venetoclax, etomoxir, and perhexiline. The effects of these drugs in combination were then evaluated using a clonogenic assay, which was analyzed using the ImageJ colony area plugin. PDAC cells were then exposed to the combinations and western blots were performed to evaluate changes downstream effectors. We have confirmed the expression of BCL-2 and CPT1A on the mitochondrial membrane using Westerns, rtPCR, and a PLA on several PDAC lines. Though single agent drugs had little effect on cell viability, the combination of venetoclax with CPT1A and β-oxidation inhibitors decreased colony formation in some PDAC cell lines. Western blot analysis revealed the drug combinations affected the phosphorylation of AKT and 4E-BP1 and expression of the pro-apoptotic protein BID. These data suggest that co-targeting BCL-2 and CPT1A have potential for anti-tumor effects in PDAC. Additional research into the role of CPT1A in PDAC biology will elucidate the optimal dosing concentrations and mechanisms for further studies.

Citation Format: Sarah J. Hartman, Nathalie Nadales, Stacey M. Bagby, Betelehem W. Yacob, Brian L. Gittleman, Adriana Estrada-Bernal, Anh T. Le, Christopher H. Lieu, S. Lindsey Davis, Alexis D. Leal, Jennifer R. Diamond, Wells A. Messersmith, Isabel R. Schlaepfer, Todd M. Pitts. Therapeutic targeting of lipid oxidation and apoptosis in pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6387.

Abstract 6647: Sensitizing microsatellite stable colorectal cancer to immune checkpoint therapy utilizing Wnt pathway inhibition

Immunotherapies that target immune regulatory checkpoints such as CTLA-4 and PD-1 are widely used among many cancer types and have shown positive results in CRC with high microsatellite instability. However, in microsatellite stable (MSS) CRC there is a dismal response rate of 0%. The limited efficacy has shown to be partially due to the lack of T-cells in the tumor microenvironment and/or no activation/regulation of paramount cells in the immune system. The Wnt pathway is the most commonly altered pathway in CRC and is highly involved in driving tumor initiation and progression. Recent evidence also demonstrates the Wnt pathway is involved in T-lymphocyte development, maturation/activation of CD8+ effector T cells and recruitment of dendritic cells. Therefore, targeting the Wnt pathway utilizing a Porcupine (PORCN) inhibitor (ETC-159) in MSS CRC may be a promising strategy to sensitize tumors to immune checkpoint inhibition.

Human Immune System BRGS (BALB/c, Rag2−/−, IL2RγC−/−, NODSIRPα) mice were engrafted with MSS CRC PDX (hPDX). The hPDX were randomized according to human chimerism into the following drug treatments groups: Vehicle, ETC-159, nivolumab, and the combination. Treatments began when tumors reached 100-300mm3 and tumors were measured twice weekly. At the end of study, sera, lymph nodes, spleen, and tumor tissue were collected for immunohistochemistry, single cell suspensions, and flow cytometry analysis.

Combination therapy resulted in a significant decrease in tumor volume compared to both single agents and vehicle. Flow cytometric analysis demonstrated an increase in human immune cells, in particular human CD4 and CD8 cells in the combination compared to the vehicle and nivolumab treated groups. Additionally, these T-cells showed increased signs of activation and effector function, as indicated by increased CD69+ expression, effector memory subsets, and granzyme B+ cells in the TILs, with a further reduction in Treg populations, suggesting an overall increase in inflammation. An increase in MHC II expression on tumor cells was observed in the ETC-159 single agent with a statistically significant increase in the combination treated tumors demonstrating enhanced antigen presentation. Furthermore, PD-1 expression was upregulated on CD4+ T-cells in the ETC-159 single agent. Lastly, VECTRA analysis corroborates the flow cytometry data showing a changing tumor immune landscape through an increase in CD4+ and CD8+ T cells in the tumor and surrounding stroma.

Our data demonstrates the combination treatment of ETC-159 + nivolumab in MSS CRC hPDX show increased tumor infiltration of human immune cells. Further preclinical data is compulsory but these results support further development of this combination in clinical trials.

Citation Format: Stacey M. Bagby, Sarah J. Hartman, Natalie M. Navarro, Betelehem W. Yacob, Jeremy Shulman, Jessica Barkow, Christopher H. Lieu, S. Lindsey Davis, Alexis D. Leal, Wells A. Messersmith, Angela Minic, Kimberly R. Jordan, Julie Lang, Todd M. Pitts. Sensitizing microsatellite stable colorectal cancer to immune checkpoint therapy utilizing Wnt pathway inhibition [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6647.

A phase 1b dose escalation study of Wnt pathway inhibitor vantictumab in combination with nab-paclitaxel and gemcitabine in patients with previously untreated metastatic pancreatic cancer

Vantictumab is a fully human monoclonal antibody that inhibits Wnt pathway signaling through binding FZD1, 2, 5, 7, and 8 receptors. This phase Ib study evaluated vantictumab in combination with nab-paclitaxel and gemcitabine in patients with untreated metastatic pancreatic adenocarcinoma. Patients received vantictumab at escalating doses in combination with standard dosing of nab-paclitaxel and gemcitabine according to a 3 + 3 design. A total of 31 patients were treated in 5 dosing cohorts. Fragility fractures attributed to vantictumab occurred in 2 patients in Cohort 2 (7 mg/kg every 2 weeks), and this maximum administered dose (MAD) on study was considered unsafe. The dosing schedule was revised to every 4 weeks for Cohorts 3 through 5, with additional bone safety parameters added. Sequential dosing of vantictumab followed by nab-paclitaxel and gemcitabine was also explored. No fragility fractures attributed to vantictumab occurred in these cohorts; pathologic fracture not attributed to vantictumab was documented in 2 patients. The study was ultimately terminated due to concerns around bone-related safety, and thus the maximum tolerated dose (MTD) of the combination was not determined. The MAD of vantictumab according to the revised dosing schedule was 5 mg/kg (n = 16).