Sideras, Kostandinos

Abstract Background: Residual disease after neoadjuvant chemotherapy (NAC) in breast cancer (BC) confers poor outcomes. Trastuzumab emtansine (T-DM1) is approved for HER2+ patients with residual disease after NAC. However, many patients still develop recurrence. H2NVAC is a multi-epitope CD4 helper T cell activating vaccine that includes a pool of 4 degenerate HER2-derived HLA-DR epitopes admixed with GM-CSF. Our previous phase I trial showed that this vaccine was safe and generated robust, long-lasting T and B cell immune responses. Method: We conducted a safety run-in phase of H2NVAC in combination with T-DM1 in stage II-III HER2+ BC with residual disease after NAC. Patients were treated with H2NVAC and T-DM1 for 6 cycles, followed by 2 boosters at 3 and 12 months. Dose-limiting toxicity (DLT) was defined as any grade (G) ≥ 3 toxicity occurring within 21 days after the first vaccination. Results: 20 patients were enrolled (median age 51; 27-69 years), including 80% White and 15% Black. 90% had hormone receptor-positive disease. There was no DLT observed in the safety run-in cohort. All adverse events (AEs) during the DLT period were grades 1 and 2, with fatigue being the most common (60% G1, 5% G2), followed by peripheral sensory neuropathy (55% G1, 5% G2), and injection site reaction (50% G1). Across all treatment cycles, the 10 most common AEs that were at least possibly related to treatment in all cycles are summarized in the table below. The injection site reaction was the most common AE, with 85% G1 and 15% G2. Conclusion: H2NVAC, in combination with T-DM1, was safe, with a favorable side effect profile. There was no DLT observed. The most common AE was injection site reaction, with the majority being G1. A multicenter, randomized, placebo-controlled, phase II trial of H2NVAC vs. placebo in combination with trastuzumab emtansine is currently ongoing through the ACCRU consortium (NCT04197687). Adverse Events Grades 1 2 N % N % Injection site reaction 17 85.0 3 15.0 Aspartate aminotransferase increase 13 65.0 Alanine aminotransferase increase 9 45.0 Fatigue 7 35.0 2 10.0 Peripheral sensory neuropathy 7 35.0 2 10.0 Alkaline phosphatase increase 8 40.0 Nausea 7 35.0 1 5.0 Arthralgia 7 35.0 Myalgia 5 25.0 1 5.0 Platelet count decrease 6 30.0 Citation Format: Saranya Chumsri, Sharmila Giri, Andy J. Ness, David W. Hillman, Nadine Norton, Davitte Cogen, Brian M. Necela, Aziza Nassar, Donald W. Northfelt, Pooja Advani, Rohit Rao, Kostandinos Sideras, Alvaro Moreno-Aspitia, Brenda J. Ernst, Kathryn J. Ruddy, Matthew P. Goetz, Keith L. Knutson. Safety and tolerability of multi-epitope HER2 peptide vaccines in combination with trastuzumab emtansine in HER2-positive breast cancer patients with residual disease after neoadjuvant chemotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5005.

Abstract Background: Activation of the RAS/MAPK pathway is associated with reduced tumor-infiltrating lymphocytes and poor outcomes in triple-negative breast cancer (TNBC). This trial evaluated the efficacy of pembrolizumab and MEK inhibitor, binimetinib. Here we evaluated potential biomarkers in peripheral blood to predict response. Methods: Patients with unresectable locally advanced or metastatic TNBC with ≤ 3 prior lines of therapy were enrolled. Treatment includes a 2-week run-in with binimetinib followed by pembrolizumab. There were 2 dose levels (DL) with binimetinib at 45 mg at DL 0 and 30 mg at DL -1. A standard 3+3 design was used in phase I, and Simon’s two-stage Optimal design was used in phase II. Circulating tumor cells (CTC) and circulating cancer-associated macrophage-like cells (CAML) were isolated using CellSieve microfilters and immunofluorescently labeled with PD-L1 and p-ERK. Wilcoxon rank sum test and Cox regression model were used for analysis. Results: A total of 22 patients were enrolled, with a median age of 58 years old. Dose-limiting toxicity (DLT) was observed in 2 out of 4 patients in DL 0, with grade 3 ALT abnormality, flank pain, and nausea. In the next 6 patients in DL -1, there was 1 DLT with grade 3 AST/ALT abnormality. There were 17 patients treated with DL -1 and were evaluable for response. The objective response rate (ORR) was 29.41% (95% CI: 10.31-55.9) with 1 complete response (CR) and 4 partial responses (PR). The clinical benefit rate (CBR ≥ 24 weeks) was 35.29% (95% CI: 14.21-61.67). ORR in patients without liver metastases was 55.56% (95% CI: 21.20 - 86.30), and CBR was 66.67% (95% CI: 29.93-92.51). There was no response observed in all 5 patients with liver metastases. Baseline mean CTC count was 1.3 cells, and CAML count was 8.9 cells/7.5 mL. Baseline PD-L1 in CAML (p 0.04) and decline in CAML size (p 0.02) after 1 cycle were significantly associated with CBR. However, baseline CTC count, CAML count (p 0.64), CAML size (p 0.46), p-ERK in CAML (p 0.23), and changes in CTC count, CAML count (p 0.83), p-ERK (p 0.07), and PD-L1 (p 0.08) in CAML were not significantly associated with responses. Using Cox regression analysis, a reduction in CAML count (p 0.02), CAML size (p 0.01), and PD-L1 in CAML (p 0.03) were associated with significant improvement in overall survival but not the reduction in p-ERK (p 0.6). Conclusions: Pembrolizumab and binimetinib at 30 mg are safe with manageable toxicities. Promising activity was observed in patients without liver metastases. Baseline PD-L1 expression, early reduction in CAML count, size, and PD-L1 expression were significantly associated with subsequent responses, providing potential noninvasive biomarkers to predict response to this combination. Future larger clinical trials are warranted to further evaluate the efficacy of this combination. Citation Format: Saranya Chumsri, Joseph J. Larson, Daniel L. Adams, Kathleen S. Tenner, Cha-Mei Tang, Morgan T. Weidner, Amanda N. Arnold, Dana L. Haley, Pooja Advani, Kostandinos Sideras, Alvaro Moreno-aspitia, Edith A. Perez, Keith L. Knutson. Peripheral blood biomarkers in Phase II study of pembrolizumab in combination with oral binimetinib in patients with unresectable locally advanced or metastatic triple-negative breast cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5454.

e24161 Background: Pertuzumab-induced gastrointestinal toxicities (PIGT), particularly diarrhea, is the most common adverse event reported in over 70% of patients receiving pertuzumab in combination with chemotherapy. PIGT can result in dose reduction, treatment delay, and discontinuation of chemotherapy. Rifaximin is a minimally absorbed oral antibiotic approved for gastrointestinal tract infections and bacterial overgrowth. Our aim was to evaluate the efficacy of rifaximin in reducing PIGT. Methods: Patients with stage I-III HER2-positive (HER2+) breast cancer who received pertuzumab in combination with docetaxel, carboplatin, and trastuzumab (TCHP) were enrolled. PIGT included diarrhea, abdominal distention, abdominal pain, dyspepsia, stomach pain, and typhlitis. Patients with any PIGT ≥ grade 2 after the first cycle of TCHP received rifaximin 550 mg orally twice daily on days 1-5 in all subsequent cycles of chemotherapy. Patients with PIGT grade < 2 were observed without rifaximin. Simon's Two-Stage design was used. Results: Between 2018-2022, a total of 21 patients were enrolled. One patient was excluded due to significant anemia not meeting the eligibility criteria to proceed with rifaximin after the first cycle of TCHP. Of 20 patients, the median age was 52.5 (39-69) years. 18/20 (90.0%) patients had PIGT ≥ grade 2 after 1 cycle of TCHP with PIGT grade 2 in 15 (83.3%) and grade 3 in 3 (16.7%). PIGT ≥ grade 2 included diarrhea in 14 (70.0%) with grade 2 in 12 (60.0%) and grade 3 in 2 (10.0%), abdominal pain in 9 (45.0%) with grade 2 in 8 (40.0%) and grade 3 in 1 (5.0%), abdominal distension in 3 (15.0%), dyspepsia in 5 (25.0%), and stomach pain in 4 (20.0%) patients. Among 18 patients who received rifaximin, 15 (83.3%; 95% CI 0.586-0.964) had at least 1 cycle with a maximum PIGT grade < 2. This result surpassed the threshold of the Two-Stage analysis. Reduction of individual PIGT symptoms for patients who experienced > grade 2 at baseline after the first cycle of rifaximin was reported in 2/3 (66.7%) for abdominal distention, 8/9 (88.9%) for abdominal pain, 6/14 (42.9%) for diarrhea, 3/4 (75.0%) for stomach pain, and 4/5 (80.0%) for dyspepsia. No patients experienced > grade 2 typhilitis at baseline and during treatment. Treatment is well tolerated, with no significant grade 3+ adverse event related to rifaximin observed. Among patients who received rifaximin, there was no treatment delay or discontinuation of pertuzumab related to PIGT. Conclusions: PIGT is a debilitating side effect observed in most patients receiving pertuzumab. A short course of rifaximin after each cycle of treatment is a well-tolerated treatment option that significantly reduces PIGT in patients receiving pertuzumab in combination with chemotherapy. Clinical trial information: NCT04249622 .

Abstract Background: Previous studies demonstrated that activation of the RAS/MAPK pathway is associated with reduced tumor-infiltrating lymphocytes and poor response to neoadjuvant chemotherapy in triple-negative breast cancer (TNBC). Further in vivo study showed that inhibition of the MAPK pathway with a MEK inhibitor is synergistic with immune checkpoint inhibitors (ICIs). Methods: Patients with unresectable locally advanced or metastatic TNBC with ≤ 3 prior lines of therapy were treated with pembrolizumab 200 mg every 3 weeks plus an oral MEK inhibitor binimetinib. Treatment was started with a 2-week run-in period with single-agent binimetinib. There were 2 dose levels in phase I, including dose level 0 (DL 0) with binimetinib at 45 mg orally twice daily continuously and dose level -1 (DL -1) at 30 mg twice daily. A standard 3+3 design was used in phase I to identify the recommended phase II dose (RP2D) and Simon’s two-stage Optimal design was used in phase II. Results: A total of 22 patients were enrolled. The median age was 58 years old (range 37-77). 14 (63.6%) patients had no prior systemic therapy in the metastatic setting and 8 (36.4%) patients had 1-2 prior lines of therapy. There were 4 patients treated in DL 0. Dose-limiting toxicity (DLT) was observed in 2 out of 4 patients in DL 0 with grade 3 ALT abnormality in one patient and grade 3 flank pain together with grade 3 nausea and vomiting &gt; 48 hours despite anti-emetic therapy in the other patient. Binimetinib dose was reduced to DL -1. In the next 6 patients, there was 1 DLT observed with grade 3 AST/ALT abnormality. Thus, DL -1 was the RP2D, and an additional 12 patients were treated with DL -1 in phase II. Overall, 18 patients were treated in DL -1 and were included in phase II efficacy evaluation. 17 patients were evaluable for response. Objective responses were observed in 5 patients (29.41% 55.96) with 1 complete response (CR) and 4 partial responses (PR). The clinical benefit rate (CBR) was 35.29% (95% CI: 14.21 - 61.67) with 6 out of 17 having had CR, PR, or stable disease &gt;= 24 weeks. Since previous studies showed poor responses to ICIs in patients with liver metastases due to macrophage-mediated T cell elimination, we further conduct exploratory analysis to evaluate responses among patients with and without liver metastases. Among all 5 patients with liver metastases, no response was observed. The objective response rate (ORR) in patients without liver metastases was 55.56% (95% CI: 21.20 - 86.30) and CBR was 66.67% (95% CI: 29.93-92.51), when excluding 3 patients who discontinued treatment due to adverse events prior to follow-up scans. Median progression-free survival in DL 0 was 2.4 (95%CI: 0.5-NE) and in DL -1 was 8.3 (95% CI: 3.9-NE) months. Median overall survival in DL 0 was 7 (95%CI: 0.5-NE) and in DL -1 was 33.2 (95% CI: 10.3-NE) months. Among patients who responded, 3 out of 5 (60%) had a duration of response greater than 12 months and ongoing even after stopping treatment (range: 5.4 - 32.0 months). Adverse events (AEs) were mostly grade 1-2 including anemia, CPK increase, fatigue, diarrhea, nausea, peripheral neuropathy, acneiform rash, AST increase, cardiac troponin increase, and constipation. Additional correlative studies are ongoing and will be presented at the meeting. Conclusions: Pembrolizumab in combination with binimetinib at 30 mg twice daily appears to be safe with manageable toxicities. Promising activity with durable responses was observed with this combination without chemotherapy, particularly in patients without liver metastases. Future studies are warranted to further evaluate the efficacy of this combination. Citation Format: Saranya Chumsri, Joseph J. Larson, Kathleen S. Tenner, Jun He, Mei-Yin Polley, Morgan T. weidner, Amanda N. Arnold, Dana Haley, Pooja Advani, Kostandinos Sideras, Alvaro Moreno-Aspitia, Edith A. Perez, Keith L. Knutson. Phase I/II study of pembrolizumab in combination with oral binimetinib in patients with unresectable locally advanced or metastatic triple-negative breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-01-17.

Abstract Background Metaplastic breast cancer (MBC) is a rare and aggressive subtype of breast cancer (BC) defined by presence of both epithelial and mesenchymal components. Most are triple negative but are often chemo-refractory and associated with poor survival outcomes compared to non-metaplastic triple negative BC. Advances in therapy have led to improvements in survival outcomes of patients (pts) with BC over the last decade. Our multicenter retrospective study aims to assess (1) progression free survival (PFS) and overall survival (OS) (2) factors predictive of survival outcomes in MBC pts Methods We performed a retrospective analysis of pts diagnosed with MBC from 1997-2021 at Mayo Clinic (Florida, Arizona and Rochester) under IRB approval. Kaplan-Meier method was used to estimate OS and PFS at 1, 3 and 5 years. Cox regression models were used to examine the association between risk factors and survival outcomes. All tests were two-sided with p value &lt; 0.05 considered statistically significant Results We evaluated 158 pts with MBC. Median age and tumor size was 61 (range: 20-91) years and 2.8 (range: 0.5-21) cm, respectively, with 80% of pts being postmenopausal. At diagnosis, 14.6% of pts had clinical T3/T4 disease, 16.4% were clinically node-positive, and 6.3% (10 pts) had distant metastases (DM). Spindle cell histology was seen in 36 pts. Most MBC pts were triple-negative (68.3%), high grade (77.2%) and high Ki-67 (36/47; 76.5%). Of the 61 pts tested for germline mutation, 8 (13.1%) were positive, with BRCA1/2, PTEN, NBN, CHEK2, and BARD1 mutations. Most pts had lumpectomy (53.8%), followed by simple mastectomy (38.5), and modified radical mastectomy (7.7%). Majority of pts had sentinel lymph node biopsy (71.8%). Adjuvant radiation therapy was performed in 65.6% of pts. Pathologic complete response (pCR) was noted in 4/38 (10.5%) evaluable pts who received neoadjuvant chemotherapy (NACT). Residual cancer burden (RCB) scores of 2 and 3 were seen in 76.2% of evaluable pts. Median follow-up time was 2.2 years (range: 6 days-24.6 years). Overall, 1-, 3-, and 5-year OS was 93.3%, 81.7%, and 76.0%, while PFS was 80.8%, 67.9%, and 60.9%, respectively. The presence of DM at diagnosis [HR 38.55 (11.18, 132.93), p &lt; 0.001] and spindle cell histology (SC) [HR 2.57 (1.19, 5.53), p = 0.02] predicted worse OS in multivariable analysis. Inferior PFS was predicted by DM [HR 18.84 (6.53, 54.35), p &lt; 0.001], SC [HR 2.46 (1.25, 4.86), p = 0.009], and node-positivity at diagnosis [HR 3.65 (1.5, 8.89), p = 0.004]. The 5-year OS and PFS were 22.2% and 0% for DM pts versus 80.0% and 65.6% for non-DM pts. The 5-year OS and PFS were 71.5% and 54.7% for SC pts versus 81% and 66.6% for non-SC pts. 5-year OS and PFS for NACT pts was 67.3% and 52.6% for NACT pts versus 78.2% and 62.8% for non-NACT pts. Age at diagnosis, menopausal status, family history of BC, grade, stage, tumor size, hormone-receptor and HER2 status, and use of NACT were not found to be significantly associated with OS or PFS in multivariate analysis. Conclusion This study is one of the largest and most recent review of institutional experiences with MBC. Overall, OS at 5 years was improved compared to prior older studies of MBC but still remains very low for those with DM, representing an area of unmet clinical need. SC and DM correlated with worse outcomes for both PFS and OS. Additionally, node positivity at diagnosis was a predictor of worse PFS. In contrast, no association was seen between survival and tumor size, stage, hormone receptor-positivity, HER2 receptor-positivity. The low pCR rates following NACT in our study are consistent with reported literature. Further, use of NACT does not impact survival, suggesting pts with resectable disease should proceed with surgery first. Citation Format: Siven Chinniah, Raza Zarrar, Zhuo Li, Kostandinos Sideras, Alvaro Moreno-Aspitia, Saranya Chumsri, Rohit Rao, Sarah McLaughlin, James Jakub, Emmanuel Gabriel, Sanjay Bagaria, Laura Vallow, Santo Maimone, Pooja Advani. Clinical Factors associated with Survival Outcomes in Patients with Metaplastic Breast Cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-05-25.

Abstract Introduction: We performed matched case-control studies utilizing cohorts of postmenopausal women with ER+ breast cancer receiving adjuvant aromatase inhibitors (AI) on MA.27 [anastrozole, exemestane] or PreFace [letrozole] to assess the association between estrogen suppression after 6 months of treatment and an early breast cancer (EBC) event within 5 years of AI initiation (Clin Cancer Res 2020;26:2986-98). We found a significant 3.0-fold increase in risk of an EBC event for those taking anastrozole with levels of estrone (E1) ≥1.3 pg/mL and estradiol (E2) ≥0.5 pg/mL, but not for exemestane or letrozole. Given these findings we designed a prospective pharmacodynamic (PD) study to evaluate the impact of anastrozole (1 mg/day: ANA1) on E1 and E2 levels, and among those with inadequate estrogen suppression (IES: E1 ≥1.3 pg/mL and E2 ≥0.5 pg/mL), to evaluate the safety and PD efficacy of high-dose anastrozole (10 mg/day: ANA10), which has been found to be safe in prior clinical trials (Cancer 1998;83:1142-52). Methods: Post-menopausal women with stage I-III, ER ≥1% positive/HER2-negative breast cancer who were candidates for anastrozole were eligible after completion of locoregional therapy and chemotherapy, as clinically indicated. Women who were pre-menopausal at diagnosis were not eligible. All patients received 8-10 weeks of ANA1, after which those with adequate estrogen suppression (AES: E1&lt; 1.3 pg/mL or E2&lt; 0.5 pg/mL) came off study. Those with IES went on to receive ANA10 for 8-10 weeks, followed by letrozole (2.5 mg/day: LET) for 8-10 weeks. All patients were managed at their treating oncologist’s discretion following study discontinuation. E1 and E2 blood levels were measured pre-treatment and after completion of each treatment cycle by a CLIA-approved liquid chromatography with tandem mass spectrometry in the Immunochemical Core Laboratory at Mayo Clinic. With a sample size of 29 patients with IES after ANA1, a one-sided binomial test of proportions with a significance level of 0.05 will have an 87% chance of rejecting the proportion with AES after ANA10 is at most 25% (Ho) when the true proportion is at least 50%. Specifically, the null hypothesis is rejected if the number of women with AES after ANA10 is 12 or more. Data lock was July 6, 2022. Results: Of the 161 women enrolled from April 2020 through May 2022, 3 withdrew consent prior to start of ANA1 and 2 were ineligible; thus, 156 women comprised the study cohort. Median patient age was 64 years (range 44-86), 10% of patients were of Hispanic ethnicity and/or non-white race, and 15% received chemotherapy. Six patients remain on ANA1, and 10 discontinued ANA1 due to refusal (7), adverse event (AE) (2), or COVID-19 (1). Forty-one of the remaining 140 patients (29.3%; 95%CI: 21.9-37.6%) had IES with ANA1. Nine of these 41 patients did not go on to ANA10 due to refusal (6) or AE (3). Of the 32 patients who started ANA10, 8 remain on treatment, 5 discontinued due to refusal (3) or AE (1-grade 2 urinary tract infection; 1-grade 1 palpitations), and 19 had a blood draw 45 days or more after starting ANA10. No grade 3-5 AEs or grade 2 hot flashes or arthralgias were reported. Of these 19 patients, 14 achieved AES with ANA10 (73.7%; 95%CI: 48.8-90.9%). All 19 patients switched to LET of which 3 remain on treatment, 1 is missing E1/E2 data, and 15 had a blood draw 45 days or more after starting LET. Of these 15 patients, 10 maintained AES, 2 acquired AES with LET, and 3 no longer had AES. Anastrozole and letrozole drug levels will be reported at the meeting. Conclusions: Approximately 29% of postmenopausal women with ER+/HER2- BC receiving adjuvant anastrozole 1 mg/daily had IES. A majority of these patients achieved AES with dose escalation to ANA10 without tolerability issues. E1 and E2 levels are logical biomarkers given the mechanism of action of anastrozole, and further study utilizing them to determine the optimal dose of anastrozole for a given patient should be performed. Citation Format: Tufia C. Haddad, Vera Suman, Karthik V. Giridhar, Alvaro Moreno-Aspitia, Donald Northfelt, Brenda Ernst, Kostandinos Sideras, Ciara C. O’Sullivan, Ravinder Singh, Zeruesenay Desta, Jodi Taraba, Barbara Goodnature, Matthew P. Goetz, Liewei Wang, James N. Ingle. Anastrozole dose escalation for optimal estrogen suppression in postmenopausal early stage breast cancer: A prospective trial [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT1-04-02.

TPS610 Background: Several studies demonstrated worsening disease-free survival in patients who failed to achieve complete pathological response after neoadjuvant chemotherapy (NAC), particularly in HER2-positive (HER2+) breast cancer. Despite the recent approval of trastuzumab emtansine (T-DM1) in patients with residual disease after NAC approximately 12% of patients still develop recurrent and metastatic disease. TPIV100 is a multi-epitope vaccine that includes a pool of 4 degenerate HER2-derived HLA-DR epitopes, which activate CD4 helper T cells, admixed with GM-CSF. In our previous phase I trial this vaccine was shown to be safe in combination with trastuzumab in stage II-III HER2+ breast cancer after completion of standard of care chemotherapy. Furthermore, this vaccine also generated robust long-lasting T-cell immune responses and antibody immunity against HER2. Methods: This trial is a multi-center, randomized, placebo-controlled, phase II trial of TPIV100 in combination with T-DM1 in stage II-III HER2+ breast cancer patients with residual disease after NAC. This trial is currently opened through the ACCRU consortium. Eligible patients include those with stage II-III HER2+ with residual disease, in the breast and/or lymph nodes, after trastuzumab ± pertuzumab-based NAC, with ECOG PS ≤ 2 and adequate organ function. Patients with baseline left ventricular ejection fraction < 50%, history of trastuzumab-related cardiac toxicity, myocardial infarction or stroke < 6 months, history of congestive heart failure, autoimmune disease, immunocompromised patients with known HIV or those on chronic steroid, hypersensitivity to GM-CSF, and other active malignancy < 3 years are excluded. TPIV100 or placebo, in combination with GM-CSF, will be given concurrently with T-DM1. To ensure that TPIV100 in combination with T-DM1 is safe, there is a run-in phase with 20 patients treated with the combination. If there is no significant dose-limiting toxicity observed in the run-in phase, the trial will be expanded to the randomized phase II portion, which will include 240 patients. Eligible patients will be randomized in a 2:1 fashion with ER/PR as a stratification factor. The primary endpoint is invasive disease-free survival, and the secondary endpoint includes immunogenicity of TPIV100 as assessed by IFN-g ELIspot analysis. Correlative studies include assessment of helper T-cell response distribution (including Th1, Th2, Th17, Tfh), HER2-specific antibody immunity, and HLA genotype. Currently, 20 patients in the run-in phase have been enrolled. Enrollment to the randomized phase II portion is expected to begin in March 2022. Clinical trial information: NCT04197687.

Abstract Background: FGFR dysregulation is observed in multiple cancers and targeting FGFR is an emerging therapeutic strategy with FDA approved treatments in bladder and cholangiocarcinoma. Here we examined the prevalence of FGFR mutations, fusions, and high-level amplifications in breast cancer, stratified by receptor subtype and local/metastatic status, in both Foundation Medicine (FM) and institutional Mayo Clinic (MC) cohorts. Methods: For the FM cohort, comprehensive genomic profiling (CGP) examining at least 324 genes for all classes of alterations, including FGFR1-4 was carried out for 32,048 breast cancers during the course of routine clinical care in a Clinical Laboratory Improvement Amendments (CLIA)-certified lab (Foundation Medicine Inc., Cambridge, MA, USA). Tumor mutational burden (TMB) was determined on up to 1.1 Mb, microsatellite instability high (MSI-High) was determined on up to 114 loci and predicted ancestry from &gt;10,000 SNPs. Estrogen receptor (ER) and HER2 status were available for a subset of FM samples. Additionally, 131 patients with metastatic breast cancer from a subset of patients at three Mayo Clinic sites (MC cohort) with clinical characteristics and cancer-panel DNA sequencing data from a CLIA-certified lab (Tempus, Chicago, IL) were included. Results: In the FM cohort, the prevalence of FGFR1-4 high-level amplification (CN≥10) was 10.1%, while mutations (1.5%) and fusions (0.72%) were rare. Most amplifications occurred in FGFR1 (9.2%); most fusions and mutations occurred in FGFR2 (0.46%, 0.77%). FGFR alteration prevalence was highest in ER+/HER2- subtype (14.4%) and lowest in HER2+ disease (7.7%). FGFR alterations were more common in IDC (11.7%) than ILC (7.7%), p&lt;3E-08. FGFR alterations were more prevalent in the metastatic setting relative to breast-biopsied disease (13.6% v 10.1%; OR = 1.4; p=2E-17), especially in the HER2+ (OR =1.9, p=0.004) and ER-/HER2- (OR = 1.9, p = 0.05) disease; no enrichment was seen in the ER+/HER2- metastases (OR =1.0, p = 1). FGFR amplifications were observed at a higher prevalence in patients with predicted East Asian ancestry, relative to patients with European ancestry (12.1% v 10.0%; p = 0.03). Overall, the most common activating mutations in FGFR were FGFR2 N549K (n=85), FGFR1 N546K (n=78), FGFR4 V510M (n=28), FGFR2 K659E (n=28), FGFR4 V510L (n=20), and FGFR2 Y375C (n=15). The most common recurrent fusions were FGFR3:TACC3 (n=36), FGFR2:TACC2 (n=17), FGFR1:TACC1 (n=9), FGFR1:BAG4 (n=6), and FGFR2:ATE1 (n=5). In patients with FGFR amplifications, the most frequently co-occurring alterations were ZNF703 (78.4%), TP53 (51.5%), CCND1 (36.1%), FGF3/4/19 (32.9 - 34.4%), PIK3CA (30.7%), MYC (29.6%), ESR1 (17.2%), EMSY (16.3%), and PTEN (10.6%). Significant co-occurrence was observed for a number of genes including FGF3/4/19, CDK4, and CDK8 (all OR&gt;2, p&lt;1E-07); mutual exclusivity was observed with PIK3R1, BRCA1, and BRCA2 (all OR &lt;0.5, p&lt;4E-13), among other genes. In the 131 metastatic tumors from MC, the prevalence of FGFR1-4 high-level amplifications was 19.8% [FGFR1 (12.4%), FGFR2 (7.4%), and FGFR3 (0.8%)]. The prevalence of high-level FGFR amplifications did not differ by clinical subtypes: HR-/HER2- (7/31), HR+/HER2- (15/79), and HER2+ (2/11), p=0.68. Conclusions: High-level FGFR amplifications are observed in &gt;11% of breast cancers, especially the ER+/HER2- subtype, while mutations/fusions are rare. These data support the ongoing studies evaluating targeted therapies for FGFR amplified ER + breast cancer. Correlations with clinical information (MC cohort) and associations with actionable alterations are ongoing and may inform potential combination strategies. Citation Format: Karthik V Giridhar, Ethan S Sokol, Peter T Vedell, Jason P Sinnwell, Aakash Desai, Tufia C Haddad, Ciara C O’Sullivan, Roberto A Leon-Ferre, Siddhartha Yadav, Kostandinos Sideras, Brenda Ernst, Minetta C Liu, Abe Eyman Casey, Xiaojia Tang, Zoe Fleischmann, Karthikeyan Murugesan, Krishna R Kalari, Matthew P Goetz. The frequency and somatic mutation landscape of Fibroblast growth factor receptor (FGFR) alterations in breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-08-02.

Abstract Background Anthracycline use in metastatic breast cancer (MBC) is hindered by cumulative exposure limits and risk of cardiotoxicity. Pixantrone, a novel aza-anthracenedione with structural similarities to mitoxantrone and anthracyclines, is theorized to exhibit less cardiotoxicity, mainly due to lack of iron binding. We conducted a randomized phase II study to evaluate the efficacy and safety of 2 dosing schedules of pixantrone in patients with refractory HER2-negative MBC. Methods Intravenous pixantrone was administered at 180 mg/m2 every 3 weeks (group A) versus 85 mg/m2 on days 1, 8, and 15 of a 28-day cycle (group B). Primary endpoint was objective response rate (ORR) and secondary endpoints included progression-free survival (PFS), median 6-month PFS, overall survival (OS), safety, quality of life, and serial assessment of circulating tumor cells. A 20% ORR was targeted as sufficient for further testing of pixantrone in this patient population. Results Forty-five patients were evaluable, with 2 confirmed partial responses in group A and 1 in group B. The trial was terminated due to insufficient activity. Overall median PFS and OS were 2.8 (95% confidence interval [CI]: 2.0-4.1) and 16.8 (95% CI: 8.9-21.6) months, respectively. Notable overall grade 3-4 adverse events were the following: neutrophil count decrease (62%), fatigue (16%), and decrease in ejection fraction (EF) (4%). Conclusion Pixantrone has insufficient activity in the second- and third-line MBC setting. It appears, however, to have limited cardiotoxicity. (ClinicalTrials.gov ID: NCT01086605).

Abstract Background: A previous neoadjuvant study in patients with triple negative breast cancer (TNBC) demonstrated that low tumor infiltrating lymphocytes (TILs) after neoadjuvant chemotherapy is associated with a poor outcome. Activation of RAS/MAPK pathway has been associated with reduced TILs. Preclinical studies showed that MEK inhibitor enhances immune responses and is synergistic with anti PD-1/PD-L1 therapy in TNBC. Methods: The standard Phase I 3+3 study design was used. Patients with unresectable locally advanced or metastatic TNBC with ≤ 3 prior lines of therapy were enrolled. Patients received single agent binimetinib for 2 weeks prior to an addition of pembrolizumab. Dose level 0 was binimetinib at 45 mg oral twice daily continuously and dose level -1 was 30 mg twice daily. Pembrolizumab was given at a fixed dose of 200 mg every 3 weeks in both dose levels. The maximum tolerated dose (MTD) was defined as the dose level below the lowest dose that induces dose-limiting toxicity (DLT) during the first 2 cycles in at least one-third of patients. Results: A total of 12 evaluable patients were enrolled in the phase I, 4 patients in dose level 0 and 8 patients in dose level -1. In dose level 0, among 3 out of 4 patients who were evaluable for DLT, 2 patients experienced DLTs, including grade (G) 3 nausea, vomiting, abdominal pain and G3 ALT elevation. Thus, the stopping rule was met and the dose level was adjusted to dose level -1. None of the first 3 patients in dose level -1 experienced a DLT. All three experienced other ≥ G3 AEs, including 1 G3 cardiac troponin T increased and 2 with G3 hypertension. 5 additional patients were accrued to dose level -1 and were evaluable for AEs. Three of these were evaluable for DLTs. One patient had G3 ALT/AST increase, deemed a DLT. However, this patient had liver metastasis and had G1 ALT/AST elevation at baseline. Her ALT/AST normalized in 3 weeks after treatment discontinuation and oral prednisone. Other ≥ G3 toxicities in the second group of 5 patients in dose level -1 include G3 hypertension (12.5%), nausea (12.5%), hypokalemia (12.5%), neutrophil count decrease (12.5%) dyspnea (12.5%), peripheral neuropathy (12.5%), and retinal detachment (12.5%). Since less than 1/3 of patients experienced DLT and there was no ≥ G4 AE at least possibly related to treatment over all cycles at any given dose level, the MTD was determined as dose level -1. Five patients are currently enrolled in the phase II section, and 10 more patients are needed. Objective response rate analysis will be performed once study enrollment is completed. Conclusions: The recommended phase II doses for pembrolizumab in combination with binimetinib are 200 mg every 3 weeks and 30 mg twice daily, respectively. The combination appears to be safe with manageable toxicities. Long term durable response has been observed. The phase 2 portion of this trial is currently on going. Citation Format: Saranya Chumsri, Jun He, David Hillman, Morgan Weidner, Morgan Weidner, Dana Haley, Aline Reis, Kathleen Tenner, Pooja Advani, Kostandinos Sideras, Alvaro Moreno-Aspitia, Edith Perez, Keith Knutson. Results of phase I study of pembrolizumab in combination with binimetinib in patients with unresectable locally advanced or metastatic triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT133.