Hubbard, Joleen M.

TPS258 Background: Engineered toxin bodies (ETBs) are comprised of a proprietarily engineered form of Shiga-like Toxin A subunit genetically fused to antibody-like binding domains. ETBs work through novel mechanisms of action & are capable of forcing internalization, self-routing through intracellular compartments to the cytosol & inducing potent cell-kill via the enzymatic & permanent inactivation of ribosomes. MT-5111 is a de-immunized ETB targeting HER2+ solid tumors. Its novel mechanism of action, via enzymatic ribosome inactivation, may not be subject to resistance mechanisms that exist for tyrosine kinase inhibitors, antibody-drug conjugates, or antibody modalities. MT-5111 binds an epitope on HER2, distinct from trastuzumab or pertuzumab, that may provide for combination potential with other HER2-targeting agents. MT-5111 is a 55 kilodalton protein & may have improved tumor penetration capability. The objective of this trial will be to determine the safety, tolerability, & maximum tolerated dose (MTD) of MT-5111 in patients (pts) with advanced HER2+ solid tumors. Methods: This Phase 1, first-in-human, open-label, dose escalation & expansion study will evaluate MT-5111 monotherapy in pts with HER2-positive solid tumors. The primary objective is to determine the MTD; secondary objectives include pharmacokinetics, tumor response & immunogenicity. Part 1 consists of MT-5111 dose escalation (0.5, 1.0, 2.0, 3.0, 4.5, 6.75, 10µg/kg/dose) based on a modified 3+3 design (n≤42 pts); Part 2 (dose expansion) will evaluate MT-5111 at the MTD in ≤98 pts. All pts will be administered MT-5111 over 30 min via IV infusion on Days 1, 8, & 15 of each 21-day cycle until disease progression, unacceptable toxicity, death, withdrawal of consent, or another reason for withdrawal. Part 1 will include pts with any HER2+ solid cancers. Part 2 will enroll 3 expansion cohorts: HER2+ breast (BC), HER2+ gastric or gastroesophageal junction adenocarcinomas (collectively referred as gastroesophageal adenocarcinomas [GEA]) & other HER2+ solid cancers. Immunohistochemistry (IHC) status must be 2+ or 3+, regardless of in situ hybridization (ISH) results; if no IHC is available for pts with BC or GEA, ISH criteria per the American Society of Clinical Oncology College of American Pathologists guidelines will be used. In metastatic cases, HER2 positivity must be demonstrated on metastatic lesions. Pts with HER2+ BC should have had ≥2 lines of HER2-directed therapy; pts with HER2+ GEA should have received or been intolerant to trastuzumab. Pts with evaluable disease may be included in Part 1; in Part 2, all pts must have ≥1 measurable lesion per Response Evaluation Criteria in Solid Tumors v1.1. Further details can be found on clinicaltrials.gov (NCT04029922). Enrollment, which began in September 2019, is ongoing. Clinical trial information: NCT04029922.

TPS153 Background: The clinical benefit of approved therapies in patients (pts) with metastatic colorectal cancer (mCRC) who progress on first- and second-line chemotherapy (FOLFOX and FOLFIRI) is limited. In pts with chemotherapy-refractory RAS wild type mCRC, antibodies targeting EGFR offer a monotherapy response rate of approximately 20% and a progression-free survival (PFS) of 4 months (Price 2014). HER2 is a validated target in gastric and breast cancers, with HER2 amplification occurring in ~3–5% of pts with mCRC. Tucatinib (TUC), recently approved for HER2+ metastatic breast cancer, is a tyrosine kinase inhibitor (TKI) highly selective for HER2 with minimal inhibition of EGFR. In pt-derived xenograft models of HER2+ mCRC, the combination of TUC + trastuzumab (TRAS) showed significantly greater antitumor activity compared with either agent alone (Kulukian 2020). The MOUNTAINEER trial was initiated to evaluate the efficacy and safety of TUC in combination with TRAS in pts with HER2+ RAS wild-type mCRC. Interim analysis of the initial 26 pts enrolled in MOUNTAINEER demonstrated an objective response rate (ORR) of 52.2% (12 partial responses [PRs] in 23 evaluable pts), median duration of response of 10.4 months, with a median PFS of 8.1 months and a median overall survival (OS) of 18.7 months (Strickler 2019). Based on these results, the trial was expanded to enable better estimation of ORR and safety. Methods: MOUNTAINEER (NCT03043313) is an open-label, pivotal phase 2 trial that initially consisted of a single cohort of up to 45 pts (Cohort A) treated with TUC (300 mg BID) and TRAS (8 mg/kg IV followed by 6 mg/kg IV every 3 weeks). The trial was expanded to include an additional 70 pts randomized 4:3 into 2 cohorts: Cohort B (N = 40) who will receive TUC + TRAS, and Cohort C (N = 30) who will receive TUC monotherapy. Pts in Cohort C will be treated with TUC (300 mg orally twice daily) with the option to crossover to TUC + TRAS if an objective response is not achieved by 12 weeks, or if progressive disease develops at any time. Eligible pts have RAS wild-type and HER2+ mCRC, and must have previously received regimens that include fluoropyrimidines, oxaliplatin, irinotecan, anti-VEGF therapy, and an anti-PD-1 if the tumor has dMMR proteins or is MSI-H. Pts who have received prior HER2-directed therapies are not eligible. Additionally, pts must have measurable disease and ECOG PS of 0 to 2. The primary endpoint of this trial is confirmed ORR (per RECIST v1.1) in Cohorts A + B as assessed by blinded independent central review. Secondary endpoints include duration of response, PFS, OS, and safety and tolerability. Enrollment is ongoing in the US and planned for the EU. Clinical trial information: NCT03043313.

TPS143 Background: Patients with KRAS and NRAS ( RAS) wild-type mCRC benefit from the epidermal growth factor receptor (EGFR) monoclonal antibodies (Abs) panitumumab and cetuximab, but nearly all patients experience resistance. Blood-based profiling of cell free DNA (cfDNA) can identify genomic alterations that drive acquired EGFR Ab resistance. After discontinuation of anti-EGFR Abs, acquired genomic alterations decay over time to undetectable levels. Some studies have suggested clinical benefit from EGFR Ab rechallenge, but there is limited evidence that EGFR Ab rechallenge improves survival compared to standard of care (SOC) therapies. We hypothesize that cfDNA profiling will identify patients appropriate for panitumumab rechallenge, and that these molecularly selected patients will have improved survival compared to current SOC therapies. Methods: This is a randomized phase II, open label study designed to compare the overall survival (OS) of panitumumab rechallenge versus SOC (investigator choice TAS-102 or regorafenib). Secondary objectives include comparisons of progression free survival, objective response rate, clinical benefit rate, and quality of life as measured by the linear analogue self-assessment (LASA) questionnaire. Eligible patients have radiographically measurable KRAS, NRAS, and BRAF codon 600 wild-type mCRC based on tumor tissue testing, and must have experienced progression or intolerance to treatment with a fluoropyrimidine, oxaliplatin, irinotecan, an anti-VEGF Ab, and an anti-PD-1 Ab if the tumor has mismatch repair deficiency or is MSI-H. Progression after at least 4 months treatment with an anti-EGFR Ab is required. All patients must be enrolled in the COLOMATE cfDNA screening protocol (NCT03765736) and meet molecular eligibility based on Guardant360 cfDNA profiling (absence of amplification of ERBB2, KRAS, NRAS, and MET; absence of mutations of BRAF, EGFR, ERBB2, KRAS, NRAS, and MET [mutant allele frequency > 0.5%]). Greater than 90 days must have elapsed between the most recent treatment with an anti-EGFR Ab and cfDNA profiling. Dosing for all study drugs is according to clinical SOC. 120 patients will be randomized 1:1 to panitumumab rechallenge or SOC. With 83 OS events, this study will have 80% power to detect an improvement in median OS from 6.5 to 10 months (HR=0.65; 1-sided α= 0.15). This study began enrollment in 6/2020. Recruitment is ongoing at 16 sites in the Academic and Community Cancer Research United (ACCRU) network (ACCRU-GI-1623). Clinical trial information: NCT03992456.

312 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.

239 Background: After trastuzumab (T) approval for advanced HER2-positive E/GEJ-AC, HER2 testing has increased in patients (pts) with resectable disease. Neoadjuvant carboplatin/paclitaxel chemoradiation (nCP-CRT) is a common therapy approach. We performed the largest evaluation, to our knowledge, of the prognostic impact of HER2 in E/GEJ-AC pts treated with nCP-CRT. Methods: We retrospectively reviewed medical records of all trimodality-eligible (T2+ or N+) pts with E/GEJ-AC who started nCP-CRT (usually 50.4 Gy) with planned surgery at Mayo Clinic (2014-2019). HER2 was tested using standard criteria for HER2 positivity (ie, immunohistochemistry 3+ or amplification by in situ hybridization). Clinicopathologic data and time to recurrence (TTR), disease free survival (DFS), overall survival (OS), survival after recurrence (SAR), and pathologic complete response (pCR – ie, no residual tumor in primary or nodes) were collected. Kaplan Meier and multivariate Cox analysis were used. Results: Of 161 consecutive eligible pts, HER2 status was available in 107 pts (HER2-positive n=26, HER2-negative n=81) of whom n=82 had surgery and n=19 had pCR. Most tumors were clinical T3 (80%) or N+ (81%), histologic grade 3 of 3 (62%). HER2 positivity was significantly associated with lower grade, but not with age, clinical T or N, or ECOG performance status (PS). A similar proportion of HER2-positive ( vs negative) pts had surgery. Among pts who had surgery, pCR rates were lower in HER2-positive ( vs negative) pts (11% [2/19] vs 27% [17/63]). After a median follow up of 23 mo, DFS and TTR were significantly shorter in HER2 positive ( vs negative) pts, independent of other pretreatment covariables (Table). Yet OS was comparable. Lung recurrence was enriched in HER2 positive ( vs negative) pts. Among pts with recurrence, SAR was longer in HER2-positive vs -negative pts. A total of 53% (10/19) of previously HER2-positive pts received T-based therapy after recurrence, and these pts were the drivers of favorable SAR (median 22 mo in n=10 HER2-positive pts who received T vs 11 mo in n=9 HER2-positive pts who did not receive T vs 11 mo in n=40 HER2-negative pts; P log-rank=.01). Conclusions: HER2 positivity ( vs negativity) is independently associated with shorter TTR and DFS, but more comparable OS. The adverse association of HER2 on tumor response and TTR may have been largely overcome through enhanced survival after recurrence, although OS data are maturing. These data may have implications for the design of endpoints in future curative-intent anti-HER2 trials. [Table: see text]

Abstract Purpose: We aimed to assess the concordance of colorectal cancer–associated methylated DNA markers (MDM) in primary and metastatic colorectal cancer for feasibility in detection of distantly recurrent/metastatic colorectal cancer in plasma. Experimental Design: A panel of previously discovered colorectal cancer–associated MDMs was selected. MDMs from primary and paired metastatic colorectal cancer tissue were assayed with quantitative methylation-specific PCR. Plasma MDMs were measured blindly by target enrichment long-probe quantitative-amplified signal assays. Random forest modeling was used to derive a prediction algorithm of MDMs in archival plasma samples from primary colorectal cancer cases. This algorithm was validated in prospectively collected plasma samples from recurrent colorectal cancer cases. The accuracy of the algorithm was summarized as sensitivity, specificity, and area under the curve (AUC). Results: Of the 14 selected MDMs, the concordance between primary and metastatic tissue was considered moderate or higher for 12 MDMs (86%). At a preset specificity of 95% (91%–98%), a panel of 13 MDMs, in plasma from 97 colorectal cancer cases and 200 controls, detected stage IV colorectal cancer with 100% (80%–100%) sensitivity and all stages of colorectal cancer with an AUC of 0.91 (0.87–0.95), significantly higher than carcinoembryonic antigen [AUC, 0.72 (0.65–0.79)]. This panel, in plasma from 40 cases and 60 healthy controls, detected recurrent/metastatic colorectal cancer with 90% (76%–97%) sensitivity, 90% (79%–96%) specificity, and an AUC of 0.96 (0.92–1.00). The panel was positive in 0.30 (0.19–0.43) of 60 patients with no evidence of disease in post-operative patients with colorectal cancer. Conclusions: Plasma assay of novel colorectal cancer–associated MDMs can reliably detect both primary colorectal cancer and distantly recurrent colorectal cancer with promising accuracy.

Abstract Background It is unclear whether results from recent trials of resectable pancreatic ductal adenocarcinoma (PDAC) are generalizable to older patients, who are underrepresented. We aimed to evaluate outcomes of surgery and of neoadjuvant and adjuvant therapy in older patients with resectable PDAC. Patients and Methods We included patients aged ≥65 years with upfront resectable PDAC from a prospectively maintained pancreatic cancer registry from 2007 to 2016. Patients were stratified into ages 65–75 and 75+ years. Overall survival (OS) was assessed in treatment comparisons: (A) surgery (n = 636) versus nonsurgical (n = 178), (B) neoadjuvant therapy (n = 139) versus upfront surgery (n = 497), and (C) adjuvant therapy (n = 379) versus surgery alone (n = 118). We compared neoadjuvant (n = 139) versus adjuvant therapy (n = 379) in an exploratory analysis. Results Nine hundred and three patients had a median age of 73.7 (range, 65–96.6) years. Median OS was 26.6 versus 11.9 months (adjusted hazard ratio [HRadj], 0.4; 95% confidence interval [CI], 0.31–0.52; p < .001) in Comparison A groups, 30.7 versus 25.8 months (HRadj, 0.69; 95% CI, 0.49–0.96; p = .03) in Comparison B groups, and 26.9 versus 17.4 months (HRadj, 0.62; 95% CI, 0.44–0.88; p = .008) in Comparison C groups, respectively. OS benefit in these treatment comparisons was present in age group 75+ with HRadj 0.24 (95% CI, 0.16–0.36; p < .001) in Comparison A and HRadj 0.52 (95% CI, 0.27–1; p = .049) in Comparison B, but not in Comparison C with HRadj 0.68 (95% CI, 0.43–1.08; p = .1). Statistically comparable median OS of patients who received neoadjuvant or adjuvant therapy stratified by age groups was observed. Conclusion Older patients with resectable PDAC who received surgery, neoadjuvant therapy, or adjuvant therapy appeared to have improved survival outcomes compared with those who did not receive such treatment. Implications for Practice Older patients with resectable pancreatic ductal adenocarcinoma (PDAC) in general are underrepresented in large clinical trials and less well studied in terms of the role of surgery, neoadjuvant therapy, and adjuvant therapy. This study collected data on older patients with resectable PDAC from a prospectively maintained single-institutional pancreatic cancer registry of a tertiary referral center from 2007 to 2016. It was found that, with multidisciplinary evaluation, older patients with resectable PDAC who received surgery, neoadjuvant therapy, or adjuvant therapy appeared to have improved survival outcomes compared with those who did not receive such treatment. These results are of substantial importance to practitioners who treat older patients, who are traditionally underrepresented in most clinical trials.

The NCCN Guidelines for Rectal Cancer provide recommendations for the diagnosis, evaluation, treatment, and follow-up of patients with rectal cancer. These NCCN Guidelines Insights summarize the panel discussion behind recent important updates to the guidelines. These updates include clarifying the definition of rectum and differentiating the rectum from the sigmoid colon; the total neoadjuvant therapy approach for localized rectal cancer; and biomarker-targeted therapy for metastatic colorectal cancer, with a focus on new treatment options for patients with BRAF V600E– or HER2 amplification–positive disease.

4088 Background: Methylated DNA markers (MDMs) are broadly informative for early detection of colorectal cancer (CRC) but have not been extensively studied for post-treatment surveillance and disease monitoring. We aimed to assess the feasibility of novel CRC-associated MDMs for detection of distant recurrent CRC (rCRC) in plasma. Methods: A panel of 13 MDMs previously identified to be discriminant for primary CRC was selected. In a cross-sectional analysis of plasma samples, MDMs were assayed blindly (by target enrichment long-probe quantitative amplified signal assay) from 160 age/sex-balanced patients (60 healthy controls, 60 with resected CRC and no evidence of disease (NED), and 40 rCRC after primary tumor resection). Plasma-derived carcinoembryonic antigen (CEA) was measured on all patients. Random forest modeling was used to derive a prediction algorithm of MDMs (with and without CEA) for the endpoint of rCRC relative to healthy controls. The accuracy of the algorithm was summarized as sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) with 95% confidence intervals (CI) in the test set. Results: Median patient age was 55 (interquartile range: 49-64) years. As shown in the Table below, a single MDM with the highest AUC was significantly better than CEA ( p= 0.02). On cross validation, CEA provided no additional improvement to the performance of the panel of 13 MDMs ( p= 0.2). The cross-validated panel of MDMs detected rCRC liver metastases with 96% (79-100%) sensitivity, lung metastases with 78% (40-97%) sensitivity, and peritoneal/nodal metastases with 57% (18-90%) sensitivity. Lesions with Response Evaluation Criteria in Solid Tumors sum > 4 cm were detected with 94% (73-100%) sensitivity and ≤4 cm with 78% (52-94%) sensitivity. Conclusions: Novel MDMs in plasma detect rCRC with promising accuracy. The clinical utility of MDMs for non-invasive post-treatment surveillance and treatment monitoring in CRC warrants further evaluation in longitudinal studies with sufficient follow-up to exclude sub-clinical recurrence in those with NED. [Table: see text]

4048 Background: PolyPEPI1018 is an off-the-shelf, multi-peptide vaccine containing 12 immunogenic epitopes derived from 7 cancer testis antigens (CTAs) frequently expressed in patients with CRC. Here we report the final results of the phase I study of PolyPEPI1018 vaccine as an add-on to maintenance therapy in mCRC patients. Methods: 11 patients with MSS mCRC were vaccinated with PolyPEPI1018 just after the transition to maintenance therapy with fluoropyrimidine/bevacizumab after first-line combo chemotherapy and bevacizumab. Part A: n = 5, single dose; Part B: n = 6, 3 doses, Q12W. Primary endpoint was safety. Immunomonitoring was performed at both blood and tumor levels, as well as prospectively predicted. Results: The vaccine was well tolerated; most common side effects were transient skin reactions. No vaccine-related SAE occurred. Pre-existing immune responses were boosted by the vaccine for 7/10 patients. De novo responses were also induced, overall, 80% of patients had CD8+ T cell responses against at least 3 CTAs. The magnitude of immune responses as well as the density and the ratio of CD8+/CD3+ tumor infiltrating T cells increased with multiple vaccine doses. Three patients had objective tumor response according to RECIST v1.1: one of them in the single dose group and two of them in the 3 doses group. Both patients in the 3 doses group qualified for curative surgery. One of them had no viable tumor cells in his primary tumor at the time of surgery. Post-trial follow-up revealed PFS of at least 12 months for 3 patients. mPFS was longer for patients receiving multiple doses (9.9 months) compared to single dose (6.1 months). Both measured and predicted multiantigenic immune responses tend to correlate with PFS and tumor volume reduction. Conclusions: PolyPEPI1018 was effective in restoring immunological responses to CTAs in patients’ with spontaneous immunity against. Treatment with PolyPEPI1018 vaccine and maintenance therapy was safe and demonstrated evidence of early clinical activity in MSS mCRC tumors. Data support further randomized trials with PolyPEPI1018. Clinical trial information: NCT03391232 .