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Pancreatic cancer has a complex tumor microenvironment which engages in extensive crosstalk between cancer cells, cancer-associated fibroblasts, and immune cells. Many of these interactions contribute to tumor resistance to anti-cancer therapies. Here, new therapeutic strategies designed to modulate the cancer-associated fibroblast and immune compartments of pancreatic ductal adenocarcinomas are described and clinical trials of novel therapeutics are discussed. Continued advances in our understanding of the pancreatic cancer tumor microenvironment are generating stromal and immune-modulating therapeutics that may improve patient responses to anti-tumor treatment.

PURPOSE Cancer drug development has largely shifted from cytotoxic chemotherapy to targeted treatment in the past two decades. Although previous studies have highlighted improvement in response rates in recent phase I trials, disease-focused reporting is limited. METHODS We integrated patient-level data for patients with hematologic malignancies who participated in phase I trials sponsored by the National Cancer Institute Cancer Therapy Evaluation Program between January 2000 and May 2019 and estimated the trend of grade 5 toxicity and response by disease subtype over time. RESULTS We analyzed 161 trials involving 3,308 patients, all of whom were assessed for toxicity and 2,404 of whom were evaluable for response to therapy. The overall rate of grade 5 toxicities was 1.81% (95% CI, 1.36 to 2.27), with no significant change in the rate over time. Baseline characteristics associated with higher risk of grade 5 toxicity were age and performance status ≥ 2 at enrollment. Overall response rate (ORR) and complete response (CR) rate for all trials during the study period were 25.1% and 14.7%, respectively. A significant increase in both ORR and CR rate was observed over time (ORR, 18.5% in 2000-2005, 25.9% in 2006-2012, and 50.6% in 2013-2019, P < .001). ORR in phase I trials varied across disease subtypes: 20.2% in acute myeloid leukemia, 9.1% in myelodysplastic syndrome, 43.2% in lymphoma, 42.9% in chronic lymphocytic leukemia, 15.1% in acute lymphoblastic leukemia, and 16.5% in myeloma. CONCLUSION Over time, the ORR and CR rates in phase I trials for hematologic malignancy have improved meaningfully, whereas the rate of toxicity-related death remains stable. This study provides broad experience that physicians can use when discussing the potential outcomes for patients with hematologic malignancy considering participation in phase I trials.

Background: Adenosquamous carcinoma of the pancreas (ASCP) is a very rare and highly aggressive variant of pancreatic ductal adenocarcinoma (PDA), accounting for 0.5-4% of all pancreatic cancer cases in the US. Current data indicates that epigenetic changes and Myc overexpression lead to squamous transdifferentiation of pancreatic tumor cells and development of ASCP. Minnelide is an oral anti-super-enhancer drug that inhibits Myc expression in preclinical models of ASCP. Oral Minnelide has been previously tested in the clinic where a Phase I study determined a recommended phase 2 dose of 2 mg/day. Major toxicities included neutropenia and sepsis. We hypothesize that Minnelide will be safe and effective in patients with advanced ASCP. Methods: This Phase II open label, single arm study being conducted at the NIH Clinical Center in Bethesda, MD (NCT04896073) will enroll up to 25 evaluable participants with advanced ASCP that has been previously treated. Eligibility criteria include: histologically confirmed ASCP (≥30% malignant squamous component), presence of metastatic, recurrent, or locally advanced unresectable disease, and progression or intolerance ≥1 prior systemic treatment for advanced disease. All participants will self-administer Minnelide at 2mg PO daily on days 1-21 of each 28-day cycle, for up to 12 cycles in the absence of disease progression or unacceptable toxicity. Restaging scans will be performed every 8 weeks. Optional biopsies will be requested at baseline, mid-cycle 1 and at time of progression. The primary objective is to determine the antitumor activity of Minnelide by evaluating the disease control rate. Secondary objectives are determination of drug safety in this patient population, progression free survival, and overall survival. Exploratory objectives include assessment of Minnelide effect on tumor cell epigenetics, Myc expression and immune cell populations using on-treatment tumor biopsy tissues. Changes in circulating tumor DNA and circulating immune cell populations upon treatment will also be evaluated. A Simon optimal two-stage phase II trial design will be used. If 3 of the first 12 patients experience disease control, then enrollment will continue up to 25 evaluable participants. If ≥8 of 25 participants experience disease control this would rule out an unacceptably low clinical benefit of 20% in favor of 40% (α = 0.1, β = 0.2). This trial opened for accrual in July 2021. Citation Format: Nebojsa Skorupan, Mehwish I. Ahmad, Seth M. Steinberg, Jane B. Trepel, Derek Cridebring, Haiyong Han, Daniel D. Von Hoff, Christine Alewine. A phase II trial of the super-enhancer inhibitor Minnelide in advanced refractory adenosquamous carcinoma of the pancreas (ASCP) [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2021 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2021;81(22 Suppl):Abstract nr PO-054.

3051 Background: LMB-100 recombinant immunotoxin consists of a mesothelin-binding Fab for targeting a modified Pseudomonas exotoxin A payload to tumors. Previous clinical trials demonstrated that almost all patients formed anti-drug-antibodies (ADAs) to LMB-100 that made administration beyond cycle 2 ineffective. Tofacitinib is an oral JAK inhibitor that prevented formation of ADAs against a closely related immunotoxin in pre-clinical studies. The primary objective of the dose escalation cohort was assessment of safety and tolerability of LMB-100 given with tofacitinib to patients with mesothelin-expressing solid tumors. The primary objective of the expansion cohort was to determine whether co-administration of tofacitinib delays formation of neutralizing LMB-100 ADAs. Methods: Patients (n = 13) with pancreatic adenocarcinoma and other mesothelin-expressing solid tumors (n = 3; cholangiocarcinoma, appendix, cystadenocarcinoma) were treated for up to 3 cycles with LMB-100 as a 30-minute infusion on days 4, 6, and 8 at two dose levels (100 and 140 mcg/kg) and co-treated with oral tofacitinib for the first 10 days of the cycle (10 mg BID). Results: Dose level 1 of LMB-100 was started at 100 mcg/kg one dose level below the single agent MTD. Dose escalation to 140 mcg/kg (dose level 2) resulted in DLTs in 2 of the 3 patients treated: grade 3 cardiac toxicity and grade 4 hyponatremia, both attributed to capillary leak syndrome. Ultimately, 7 patients were treated at dose level 1 without DLTs and 100 mcg/kg was chosen as the LMB-100 dose for the expansion cohort. The last of 6 patients treated in the expansion cohort developed grade 4 pericardial effusion leading to early closure of the study for toxicity. No objective responses were seen. Of the 8 patients who received two cycles of treatment at MTD, 4 met prespecified criteria for ADA prevention, and 2 patients who went on to receive cycle 3 had detectable LMB-100 plasma drug levels after administration. Conclusions: LMB-100 was unable to be co-administered safely with tofacitinib. ADA formation was prevented in 2 patients through 3 cycles, a rare occurrence. Clinical trial information: NCT04034238.

Background Phase I study is an essential step of drug development to assess safety, but more recently also to investigate initial insights into potential patient therapeutic response. In the last two decades, treatment of hematologic malignancy has changed dramatically from chemotherapy to targeted agents such as monoclonal antibodies, small molecule inhibitors and immunotherapy. We leveraged a large cohort of phase 1 studies to assess trends in toxicity, response and survival outcomes over time. Methods We reviewed the database of all investigator-initiated phase 1 oncology trials treated patients with hematologic malignancies sponsored by CTEP at the NCI between 2000 and 2019. We report the rates of grade 5 toxicity, response to treatment, and survival outcome following enrollment to the trials. Univariate associations of rates of Grade 5 toxicities possibly, probably, or definitely attributable to treatment and response rate with disease type, year of study activation, or whether each type of treatment was administered were assessed through likelihood ratio tests of a generalized linear mixed model. Results Overall, 3,308 patients were treated in 161 trials. Median age of the patients was 61 (range: 0-96) and 61% were male. Acute myeloid leukemia/myelodysplastic syndrome (AML/MDS) was the most common enrolled malignancy diagnosis (N=1,768) followed by lymphoma (N=921), acute lymphoblastic lymphoma (ALL: N=193) and myeloma (N=153). Forty percent of the trials used an investigational agent as a monotherapy, while 60% of the trials used combination treatment. The most commonly used non-chemotherapy investigational agents were monoclonal antibodies and HDAC inhibitors (28 trials each), followed by DNMT inhibitors (18 trials) and proteasome inhibitors (17 trials). Overall, 468 patients died during trials of which 60 were attributed to the treatment (grade 5 toxicity: 1.81%, 95%CI: 1.36-2.27%). There was a trend of higher grade 5 toxicity in patients with AML/MDS (2.43%) compared to patients with lymphoma (0.98%), ALL (1.55%) or myeloma (0.65%) (p=0.066). Treatment with a PD-1 inhibitor was associated with significantly higher risk of grade 5 toxicities (7.14%, 95%CI: 1.95%-12.3%), compared to patients who did not receive a PD-1 inhibitor (1.65%, 95%CI: 1.21%-2.09%) (odds ratio [OR]: 4.93, 95%CI: 1.54-15.8). The deaths mostly occurred in trials combining a PD-1 inhibitor and a CTLA-4 inhibitor (6 death in 77 pts), although the grade 5 toxicity rate did not significantly differ from PD-1 inhibitor monotherapy (1 death in 21 pts). There was no significant difference in grade 5 toxicity among the time periods when trials were activated (Table. 2000-2005 vs 2006-2012 vs 2013-2019). Baseline characteristics associated with higher risk of grade 5 toxicity were age (OR: 1.02 by 1 year increase in age, 95%CI: 1.01-1.04, p=0.007) and performance status ≥2 at enrollment (OR: 1.56, 95%CI: 1.02-2.39, p=0.039). Response assessment was available in 2,404 patients. Overall response rate (ORR) and CR rate (CRR) from all trials were 25.1% (95%CI: 23.3-26.8%) and 14.7% (95%CI: 13.3-16.2%), respectively. The patients with lymphoma experienced significantly higher ORR (42.8%) compared to patients with AML (18.2%), ALL (13.3%) or myeloma (13.3%). There is a significant increase in both ORR and CRR over time (Table. p Overall survival (OS) was available in 2,664 patients. The median OS among all patients after enrollment in phase 1 studies was 277 days (95%CI: 245-305 days). Patients with ALL had significantly shorter median OS (86 days) compared to patients with AML/MDS (255 days), lymphoma (289 days) or myeloma (median not reached). Conclusion There has been a significant improvement of ORR in CTEP sponsored phase I studies in the last 20 years. Grade 5 toxicity rate remained low, but higher age and poor performance status were associated with higher risk. Participation in phase I studies should be encouraged in patients with hematologic malignancies. Table Disclosures No relevant conflicts of interest to declare.