Preclinical and Clinical Observations Implying Combination Therapy to Enhance the Efficacy of the Her-2/neu B-Cell Peptide-Based Vaccine HER-Vaxx and to Prevent Immune Evasion

Her-2/neu-targeting therapy by passive application with trastuzumab is associated with acquired resistance and subsequent metastasis development, which is attributed to the upregulation of tumoral PD-L1 expression and the downregulation of Her-2/neu. We aimed to investigate this association, following active immunization with our recently constructed B-cell peptide-based Her-2/neu vaccines in both preclinical and clinical settings. Immunohistochemistry (IHC), fluorescence in situ hybridization (FISH), and combined positive score (CPS) were applied to evaluate Her-2/neu and PD-L1 expression using a murine syngeneic tumor model for Her-2/neu lung metastases and tumor biopsies from a gastric cancer patient with disease progression. A significant and concomitant reduction in Her-2/neu and the upregulation of PD-L1 expression was observed in vaccinated mice after 45 days, but not after 30 days, of metastases development. A significant increase in tumor-infiltrating B lymphocytes was observed at both time points. The downregulation of Her-2/neu and the upregulation of PD-L1 were observed in a patient's primary tumor at the disease progression time point but not prior to vaccination (Her-2/neu IHC: 3 to 0, FISH: 4.98 to 1.63; PD-L1 CPS: 0% to 5%). Our results further underline the need for combination therapy by targeting PD-L1 to prevent metastasis formation and immune evasion of Her-2/neu-positive and PD-L1-negative tumor cells.

HERIZON: A phase 2 study of HER-Vaxx (IMU-131), a HER2-targeting peptide vaccine, plus standard of care chemotherapy in patients with HER2-overexpressing metastatic or advanced gastric/GEJ adenocarcinoma— Overall survival analysis

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Background: Active immunization with the B-lymphocyte stimulating HER2 vaccine, HER-Vaxx (IMU-131), has shown clinical response correlated with HER2-specific antibodies (Wiedermann et. al., Clinical Cancer Research, 2021). The HER-Vaxx HERIZON study is based on the landmark ToGA study (Bang et. al., The Lancet, 2010) and included patients with HER2/neu over-expressing metastatic or advanced gastric/GEJ adenocarcinoma who were naïve to HER2 therapy. Methods: Thirty-six patients were randomized to either HER-Vaxx plus standard chemotherapy or standard chemotherapy alone. The primary endpoint was overall survival (OS). HER-Vaxx plus chemotherapy treated patients received 50 µg dose of HER-Vaxx by intra-muscular injection at Days 0, 14, 35, 77 and every 63 days until disease progression. Both groups received chemotherapy starting at Day 0 and then every 21 days for a maximum of 6 cycles or until disease progression. Standard chemotherapy consisted of cisplatin + 5FU or capecitabine, or oxaliplatin + capecitabine. Statistical analysis pre-specified a 1-sided false positive probability of 0.10. Results: Of 36 patients randomized (19 treated with HER-Vaxx plus chemotherapy and 17 with chemotherapy alone), 32 patients had a survival event (15 and 17 respectively) at the time of final analysis. All patients received oxaliplatin + capecitabine chemotherapy. Analysis showed a 42% survival benefit for patients treated with HER-Vaxx plus chemotherapy compared to chemotherapy alone. This translated into an OS HR of 0.580 (80% 2-sided CI: 0.362, 0.927) with a statistically significant p-value of 0.066. The median OS for patients receiving HER-Vaxx plus chemotherapy was 13.9 (7.5, 14.3) months, compared to 8.3 (6.0, 9.6) months in patients treated with chemotherapy alone. Median duration of response was 30 vs 19 weeks in favor of the HER-Vaxx arm. There was no difference in safety between the two treatment arms, indicating HER-Vaxx does not add toxicity to standard chemotherapy. HER-Vaxx induced persistent HER2 specific antibodies which correlated with clinical response. Additional response parameters including DOR and biomarker data will be presented at the meeting. Conclusions: These data demonstrate that in patients with HER2 over-expressing gastric/GEJ cancer active HER2 immunization with HER-Vaxx is safe and provides relevant clinical benefit over standard of care chemotherapy. Clinical trial information: NCT02795988 .

nextHERIZON: A phase 2 study of HER-Vaxx, a HER2-targeting peptide vaccine, in combination with chemotherapy or pembrolizumab in patients with HER2 metastatic or advanced gastric/gastroesophageal adenocarcinoma that progressed on or after trastuzumab treatment

TPS481

Background: HER-Vaxx is a B-cell peptide vaccine composed of a fusion of 3 epitopes from the extracellular domain of HER2/neu conjugated to CRM197 with the adjuvant Montanide. Results from a phase 1b study revealed that active immunization with HER-Vaxx was well tolerated and induced HER2-dose dependent immune responses corresponding to tumor reduction in advanced gastric cancer (GC) or gastroesophageal adenocarcinoma (GEA) (Wiedermann, 2021). A phase 2 study, HERIZON, comparing HER-Vaxx plus standard chemotherapy or chemotherapy alone is currently enrolling. Pre-clinical data demonstrated a synergistic effect with combination of HER2 and PD-1 vaccines and 90% tumor growth inhibition (Kaumaya, 2020). Ramucirumab plus paclitaxel is an approved second-line treatment for patients with GC or GEA who have failed first-line treatment chemotherapy or trastuzumab (TRA) (Wilke, 2014). The nextHERIZON study seeks to evaluate the clinical benefit of adding HER-Vaxx to ramucirumab plus paclitaxel or pembrolizumab, following progression on TRA. Methods: nextHERIZON is phase 2, open-label, non-comparative, double arm, 2-stage design study in patients with confirmed AGC and HER2 overexpression following progression on or after TRA. Arm assignment depends on prior PD-1/PD-L1 inhibitor treatment. Arm 1 will receive HER-Vaxx + ramucirumab and paclitaxel. Arm 2 will receive HER-Vaxx + pembrolizumab. Up to 55 patients will be enrolled in each arm which includes a safety run-in phase. Arms will be analyzed independently. The key inclusion criteria are: patients ³ 18 year of age; ECOG 0 or 1; minimum life expectancy of 3 months; progressed on or after TRA; confirmed HER2 overexpression; at least one measurable lesion; adequate hematologic and organ function. Key exclusion criteria include previous treatment with trastuzumab-deruxtecan or any other anti-HER2 therapy other than trastuzumab. Arm 2 excludes prior therapy with anti- PD-1, PD-L1 or PD-L2 agents. The co-primary endpoints are safety and objective response rate (RECIST 1.1). Secondary objectives are efficacy and survival measures. HER-Vaxx is administered by intramuscular (IM) injection on Day 1, Day 15, and Day 29 and on Day 1 of each 2nd or 3rd cycle depending on arm. Dose-limiting toxicity (DLT) window is 29 days on treatment. Tumor assessment is evaluated at Day 43 then every 6 weeks until progression or withdrawal. This study is currently enrolling patients in Australia and US (Q1 2023). Clinical trial information: NCT05311176 .

Coastal: A phase 3 study of the PI3Kδ inhibitor zandelisib with rituximab (R) versus immunochemotherapy in patients with relapsed indolent non-Hodgkin’s lymphoma (iNHL)

TPS7573

Background: Patients (pts) with iNHL treated with front-line immunochemotherapy may benefit from an alternative, chemotherapy-free regimen at relapse. Zandelisib, a potent, selective, and structurally differentiated oral PI3Kδ inhibitor, achieved an 87% response rate, with median duration of response not reached in iNHL when given as a monotherapy or in combination with R. A low rate ( < 10%) of Grade ≥ 3 immune-mediated adverse events of special interest associated with PI3kδ inhibitors is observed in patients administered zandelisib on an intermittent schedule (IS) (JCO 2020 38:15_suppl, 8016). An open-label, phase 2 study (TIDAL, NCT03768505) of zandelisib as monotherapy is ongoing in pts with relapsed/refractory follicular lymphoma (FL) and marginal zone lymphoma (MZL). Methods: The COASTAL study is a randomized, open-label, controlled multicenter phase 3 trial to investigate the safety and efficacy of zandelisib in combination with R versus standard immunochemotherapy in pts with iNHL. Key eligibility criteria: adults with relapsed or refractory FL or MZL who received ≥1 prior lines of therapy which must have included an anti-CD20 antibody in combination with chemotherapy or lenalidomide (L); at least one bi-dimensionally measured lesion > 1.5 cm; adequate bone marrow, renal and hepatic function; ECOG performance status score of 0 to 1. Key exclusion criteria: histologically confirmed diagnosis of FL grade 3b or transformed disease; administration of 2 prior immunochemotherapy regimens; prior PI3K inhibitor therapy; known lymphomatous involvement of the central nervous system. Subjects will be randomized 1:1 to receive R-zandelisib or immunochemotherapy (R-CHOP or R-B) and stratified by type and number of prior treatment regimens, histology, and duration of treatment-free interval after last therapy. Zandelisib will be given in a 28-day cycle comprising of daily dosing for 2 cycles followed by IS dosing on days 1-7 of each 28-day subsequent cycle for a duration of 2 years. Rituximab or immunochemotherapy will be given for a total of 6 cycles. Disease response will be assessed by an Independent Response Review Committee according to the modified Lugano Classification. Radiographic tumor assessment will be performed approximately every 12 weeks for the first 9 months, every 16 weeks for the next 12 months, and every 24 weeks thereafter. The primary efficacy endpoint is progression-free survival. The major secondary endpoints include ORR, complete response rate, overall survival, and safety. The trial will enroll approximately 534 pts in ̃200 sites globally and will begin enrollment in mid-2021. Clinical trial information: NCT04745832.

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

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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.

Peroxisome proliferator-activated receptor gamma suppresses proximal alpha1(I) collagen promoter via inhibition of p300-facilitated NF-I binding to DNA in hepatic stellate cells

Depletion of peroxisome proliferator-activated receptor gamma (PPARgamma) represents one of the key molecular changes that underlie transdifferentiation (activation) of hepatic stellate cells in the genesis of liver fibrosis (Miyahara, T., Schrum, L., Rippe, R., Xiong, S., Yee, H. F., Jr., Motomura, K., Anania, F. A., Willson, T. M., and Tsukamoto, H. (2000) J. Biol. Chem. 275, 35715-35722; Hazra, S., Xiong, S., Wang, J., Rippe, R. A., Krishna, V., Chatterjee, K., and Tsukamoto, H. (2004) J. Biol. Chem. 279, 11392-11401). In support of this notion, ectopic expression of PPARgamma suppresses hepatic stellate cells activation markers, most notably expression of alpha1(I) procollagen. However, the mechanisms underlying this antifibrotic effect are largely unknown. The present study utilized deletion-reporter gene constructs of proximal 2.2-kb alpha1(I) procollagen promoter to demonstrate that a region proximal to -133 bp is where PPARgamma exerts its inhibitory effect. Within this region, two DNase footprints with Sp1 and reverse CCAAT box sites exist. NF-I, but not CCAAT DNA-binding factor/NF-Y, binds to the proximal CCAAT box in hepatic stellate cells. A mutation of this site almost completely abrogates the promoter activity. NF-I mildly but independently stimulates the promoter activity and synergistically promotes Sp1-induced activity. PPARgamma inhibits NF-I binding to the most proximal footprint (-97/-85 bp) and inhibits its transactivity. The former effect is mediated by the ability of PPARgamma to inhibit p300-facilitated NF-I binding to DNA as demonstrated by chromatin immunoprecipitation assay.