Molecular insights into clinical trials for immune checkpoint inhibitors in colorectal cancer: Unravelling challenges and future directions

Colorectal cancer (CRC) is a complex disease with diverse etiologies and clinical outcomes. Despite considerable progress in development of CRC therapeutics, challenges remain regarding the diagnosis and management of advanced stage metastatic CRC (mCRC). In particular, the five-year survival rate is very low since mCRC is currently rarely curable. Over the past decade, cancer treatment has significantly improved with the introduction of cancer immunotherapies, specifically immune checkpoint inhibitors. Therapies aimed at blocking immune checkpoints such as PD-1, PD-L1, and CTLA-4 target inhibitory pathways of the immune system, and thereby enhance anti-tumor immunity. These therapies thus have shown promising results in many clinical trials alone or in combination. The efficacy and safety of immunotherapy, either alone or in combination with CRC, have been investigated in several clinical trials. Clinical trials, including KEYNOTE-164 and CheckMate 142, have led to Food and Drug Administration approval of the PD-1 inhibitors pembrolizumab and nivolumab, respectively, for the treatment of patients with unresectable or metastatic microsatellite instability-high or deficient mismatch repair CRC. Unfortunately, these drugs benefit only a small percentage of patients, with the benefits of immunotherapy remaining elusive for the vast majority of CRC patients. To this end, primary and secondary resistance to immunotherapy remains a significant issue, and further research is necessary to optimize the use of immunotherapy in CRC and identify biomarkers to predict the response. This review provides a comprehensive overview of the clinical trials involving immune checkpoint inhibitors in CRC. The underlying rationale, challenges faced, and potential future steps to improve the prognosis and enhance the likelihood of successful trials in this field are discussed.

Downregulation of IRF8 in alveolar macrophages by G-CSF promotes metastatic tumor progression

Tissue-resident macrophages (TRMs) are abundant immune cells within pre-metastatic sites, yet their functional contributions to metastasis remain incompletely understood. Here, we show that alveolar macrophages (AMs), the main TRMs of the lung, are susceptible to downregulation of the immune stimulatory transcription factor IRF8, impairing anti-metastatic activity in models of metastatic breast cancer. G-CSF is a key tumor-associated factor (TAF) that acts upon AMs to reduce IRF8 levels and facilitate metastasis. Translational relevance of IRF8 downregulation was observed among macrophage precursors in breast cancer and a CD68hiIRF8loG-CSFhi gene signature suggests poorer prognosis in triple-negative breast cancer (TNBC), a G-CSF-expressing subtype. Our data highlight the underappreciated, pro-metastatic roles of AMs in response to G-CSF and identify the contribution of IRF8-deficient AMs to metastatic burden. AMs are an attractive target of local neoadjuvant G-CSF blockade to recover anti-metastatic activity.

A phase Ib study evaluating the recommended phase II dose, safety, tolerability, and efficacy of mivavotinib in combination with nivolumab in advanced solid tumors

Mivavotinib (TAK-659/CB-659), a dual SYK/FLT3 inhibitor, reduced immunosuppressive immune cell populations and suppressed tumor growth in combination with anti-PD-1 therapy in cancer models. This dose-escalation/expansion study investigated the safety, pharmacokinetics, pharmacodynamics, and preliminary efficacy of mivavotinib plus nivolumab in patients with advanced solid tumors. Patients received oral mivavotinib 60-100 mg once-daily plus intravenous nivolumab 3 mg/kg on days 1 and 15 in 28-day cycles until disease progression or unacceptable toxicity. The dose-escalation phase evaluated the recommended phase II dose (RP2D; primary endpoint). The expansion phase evaluated overall response rate (primary end point) at the RP2D in patients with triple-negative breast cancer (TNBC). During dose-escalation (n = 24), two dose-limiting toxicities (grade 4 lipase increased and grade 3 pyrexia) occurred in patients who received mivavotinib 80 mg and 100 mg, respectively. The determined RP2D was once-daily mivavotinib 80 mg plus nivolumab 3 mg/kg. The expansion phase was terminated at ~50% enrollment (n = 17) after failing to meet an ad hoc efficacy futility threshold. Among all 41 patients, common treatment-emergent adverse events (TEAEs) included dyspnea (48.8%), aspartate aminotransferase increased, and pyrexia (46.3% each). Common grade ≥3 TEAEs were hypophosphatemia and anemia (26.8% each). Mivavotinib plasma exposure was generally dose-proportional (60-100 mg). One patient had a partial response. Mivavotinib 80 mg plus nivolumab 3 mg/kg was well tolerated with no new safety signals beyond those of single-agent mivavotinib or nivolumab. Low response rates highlight the challenges of treating unresponsive tumor types, such as TNBC, with this combination and immunotherapies in general. TRIAL REGISTRATION ID: NCT02834247.

Increased PIEZO1 Expression Is Associated with Worse Clinical Outcomes in Hormone-Receptor-Negative Breast Cancer Patients

PIEZO1 plays a crucial role in the human body as a mechanosensory ion channel. It has been demonstrated that PIEZO1 is important in tissue development and regulating many essential physiological processes. Studies have suggested that the PIEZO1 ion channel plays a role in invasion and progression in cancer; elevated levels of PIEZO1 have been correlated with increased migration in breast cancer cells, chemo-resistance and invasion in gastric cancer cells, and increased invasion of osteosarcoma cells. In addition, high PIEZO1 expression levels were correlated with a worse prognosis in glioma patients. On the other hand, studies in lung cancer have attributed high PIEZO1 levels to better patient outcomes. However, the clinical impact of PIEZO1 in breast cancer is not well characterized. Therefore, our goal was to determine the clinical relevance of PIEZO1 in breast cancer. An analysis of breast cancer data from The Cancer Genome Atlas (TCGA) was conducted to investigate PIEZO1 expression levels and correlation to survival, followed by validation in an independent dataset, GSE3494. We also performed gene set enrichment analysis (GSEA) and pathway enrichment analysis. We also analyzed the immune cell composition in breast tumors from TCGA through a CIBERSORT algorithm. Our results demonstrated that the PIEZO1 expression levels are higher in hormone-receptor (HR)-negative than in HR-positive cohorts. High PIEZO1 expression is correlated with a significant decrease in survival in HR-negative cohorts, especially in triple-negative breast cancer (TNBC), suggesting that PIEZO1 could be utilized as a prognostic biomarker in HR-negative breast cancer. GSEA showed that various signaling pathways associated with more invasive phenotypes and resistance to treatments, including epithelial-mesenchymal transition (EMT), hypoxia, and multiple signaling pathways, are enriched in high-PIEZO1 HR-negative tumors. Our results also demonstrated a decrease in CD8+ and CD4+ T cell infiltration in high-PIEZO1 HR-negative tumors. Further investigations are necessary to elucidate the mechanistic roles of PIEZO1 in HR-negative breast cancer.

Adaptive phase I-II clinical trial designs identifying optimal biological doses for targeted agents and immunotherapies

Targeted agents and immunotherapies have revolutionized cancer treatment, offering promising options for various cancer types. Unlike traditional therapies the principle of "more is better" is not always applicable to these new therapies due to their unique biomedical mechanisms. As a result, various phase I-II clinical trial designs have been proposed to identify the optimal biological dose that maximizes the therapeutic effect of targeted therapies and immunotherapies by jointly monitoring both efficacy and toxicity outcomes. This review article examines several innovative phase I-II clinical trial designs that utilize accumulated efficacy and toxicity outcomes to adaptively determine doses for subsequent patients and identify the optimal biological dose, maximizing the overall therapeutic effect. Specifically, we highlight three categories of phase I-II designs: efficacy-driven, utility-based, and designs incorporating multiple efficacy endpoints. For each design, we review the dose-outcome model, the definition of the optimal biological dose, the dose-finding algorithm, and the software for trial implementation. To illustrate the concepts, we also present two real phase I-II trial examples utilizing the EffTox and ISO designs. Finally, we provide a classification tree to summarize the designs discussed in this article.

Systemic infusion of TLR3-ligand and IFN-α in patients with breast cancer reprograms local tumor microenvironments for selective CTL influx

BACKGROUND

Presence of cytotoxic T lymphocytes (CTL) in the tumor microenvironment (TME) predicts the effectiveness of cancer immunotherapies. The ability of toll-like receptor 3 (TLR3) ligands, interferons (IFNs) and COX2 inhibitors to synergistically induce CTL-attracting chemokines (but not regulatory T cell (Treg)-attractants) in the TME, but not in healthy tissues, observed in our preclinical studies, suggested that their systemic application can reprogram local TMEs.

METHODS

Six evaluable patients (33-69 years) with metastatic triple-negative breast cancer received six doses of systemic chemokine-modulating (CKM) regimen composed of TLR3 ligand (rintatolimod; 200 mg; intravenous), IFN-α2b (20 MU/m2; intravenous) and COX2 inhibitor (celecoxib; 2×200 mg; oral) over 2 weeks. The predetermined primary endpoint was the intratumoral change in the expression of CTL marker, CD8α, in the post-CKM versus pre-CKM tumor biopsies. Patients received follow-up pembrolizumab (200 mg, intravenously, every 3 weeks), starting 3-8 days after completion of CKM.

RESULTS

Post-CKM biopsies showed selectively increased CTL markers CD8α (average 10.2-fold, median 5.5-fold, p=0.034) and granzyme B (GZMB; 6.1-fold, median 5.8-fold, p=0.02), but not FOXP3 (Treg marker) relative to HPRT1 expression, resulting in the increases in average CD8α/FOXP3 ratio and GZMB/FOXP3 ratio. CKM increased intratumoral CTL-attractants CCL5 and CXCL10, but not Treg-attractants CCL22 or CXCL12. In contrast, CD8+ T cells and their CXCR3+ subset showed transient decreases in blood. One clinical response (breast tumor autoamputation) and three stable diseases were observed. The patient with clinical response remains disease free, with a follow-up of 46 months as of data cut-off.

CONCLUSIONS

Short-term systemic CKM selectively increases CTL numbers and CTL/Treg ratios in the TME, while transiently decreasing CTL numbers in the blood. Transient effects of CKM suggest that its simultaneous application with checkpoint blockade and other forms of immunotherapy may be needed for optimal outcomes.

Genetic Alterations Detected by Circulating Tumor DNA in HER2-Low Metastatic Breast Cancer

PURPOSE

About 50% of breast cancers are defined as HER2-low and may benefit from HER2-directed antibody-drug conjugates. While tissue sequencing has evaluated potential differences in genomic profiles for patients with HER2-low breast cancer, genetic alterations in circulating tumor DNA (ctDNA) have not been well described.

EXPERIMENTAL DESIGN

We retrospectively analyzed 749 patients with metastatic breast cancer (MBC) and ctDNA evaluation by Guardant360 from three academic medical centers. Tumors were classified as HER2-low, HER2-0 (IHC 0) or HER2-positive. Single-nucleotide variants, copy-number variants, and oncogenic pathways were compared across the spectrum of HER2 expression. Overall survival (OS) was evaluated by HER2 status and according to oncogenic pathways.

RESULTS

Patients with HER2-low had higher rates of PIK3CA mutations [relative risk ratio (RRR), 1.57; P = 0.024] compared with HER2-0 MBC. There were no differences in ERBB2 alterations or oncogenic pathways between HER2-low and HER2-0 MBC. Patients with HER2-positive MBC had more ERBB2 alterations (RRR, 12.43; P = 0.002 for amplification; RRR, 3.22; P = 0.047 for mutations, in the hormone receptor-positive cohort), fewer ERS1 mutations (RRR, 0.458; P = 0.029), and fewer ER pathway alterations (RRR, 0.321; P < 0.001). There was no difference in OS for HER2-low and HER2-0 MBC [HR, 1.01; 95% confidence interval (CI), 0.79-1.29], while OS was improved in HER2-positive MBC (HR, 0.32; 95% CI, 0.21-0.49; P < 0.001).

CONCLUSIONS

We observed a higher rate of PIK3CA mutations, but no significant difference in ERBB2 alterations, oncogenic pathways, or prognosis, between patients with HER2-low and HER2-0 MBC. If validated, our findings support the conclusion that HER2-low MBC does not represent a unique biological subtype.

A T Cell-Engaging Tumor Organoid Platform for Pancreatic Cancer Immunotherapy

Pancreatic ductal adenocarcinoma (PDA) is a clinically challenging disease with limited treatment options. Despite a small percentage of cases with defective mismatch DNA repair (dMMR), PDA is included in the most immune-resistant cancer types that are poorly responsive to immune checkpoint blockade (ICB) therapy. To facilitate drug discovery combating this immunosuppressive tumor type, a high-throughput drug screen platform is established with the newly developed T cell-incorporated pancreatic tumor organoid model. Tumor-specific T cells are included in the pancreatic tumor organoids by two-step cell packaging, fully recapitulating immune infiltration in the immunosuppressive tumor microenvironment (TME). The organoids are generated with key components in the original tumor, including epithelial, vascular endothelial, fibroblast and macrophage cells, and then packaged with T cells into their outside layer mimicking a physical barrier and enabling T cell infiltration and cytotoxicity studies. In the PDA organoid-based screen, epigenetic inhibitors ITF2357 and I-BET151 are identified, which in combination with anti-PD-1 based therapy show considerably greater anti-tumor effect. The combinatorial treatment turns the TME from immunosuppressive to immunoactive, up-regulates the MHC-I antigen processing and presentation, and enhances the effector T cell activity. The standardized PDA organoid model has shown great promise to accelerate drug discovery for the immunosuppressive cancer.

Understanding and targeting erythroid progenitor cells for effective cancer therapy

PURPOSE OF REVIEW

It is well described that tumor-directed aberrant myelopoiesis contributes to the generation of various myeloid populations with tumor-promoting properties. A growing number of recent studies have revealed the importance of the previously unappreciated roles of erythroid progenitor cells (EPCs) in the context of cancer, bringing the updated concept that altered erythropoiesis also facilitates tumor growth and progression. Better characterization of EPCs may provide attractive therapeutic opportunities.

RECENT FINDINGS

EPCs represent a heterogeneous population. They exhibit crucial pro-tumor activities by secreting growth factors and modulating the immune response. Cancers induce potent EPC expansion and suppress their differentiation. Recent single-cell transcriptome and lineage tracking analyses have provided novel insight that tumor-induced EPCs are able to be transdifferentiated into immunosuppressive myeloid cells to limit T-cell function and immunotherapy. Therapeutic strategies targeting key factors of EPC-driven immunosuppression, reducing the amount of EPCs, and promoting EPC differentiation and maturation have been extensively investigated.

SUMMARY

This review summarizes the current state of knowledge as to the fascinating biology of EPCs, highlights mechanisms by which they exert the tumor promoting activities, as well as the perspectives on future directions and strategies to target these cells for potential therapeutic benefit.

Abstract P4-06-07: Preliminary indications of safety and efficacy of neoadjuvant chemotherapy plus chemokine-modulating regimen (rintatolimod, IFN-α2b, celecoxib) in triple negative breast cancer

BACKGROUND: Pathologic complete response (pCR) or microinvasive residual breast cancer (ypTmic) following neoadjuvant chemotherapy (NAC) is critical for good long-term outcomes in triple negative breast cancer (TNBC) patients (pts) but is achieved only in 40-50% of pts. Its combination with pembrolizumab, the new standard of care in TNBC, increases the pCR rate to 65% but is associated with significant immune-related and permanent toxicities. Higher intratumoral levels of CD8+ cytotoxic T-lymphocytes (CTLs) and low levels of regulatory T-cells (Treg) and myeloid derived suppressor cells (MDSC) predict improved relapse-free survival (RFS), overall survival (OS) and higher probability of pCR, a surrogate marker for RFS. Locally produced chemokines CCL5, CXCL9, CXCL10 and CXCL11 are critical for local infiltration with CTLs, while CCL22 is responsible for Treg attraction, with high CXCL9 expression being associated with a 3-fold higher rate of achieving pCR in response to NAC. Our preclinical data show that Chemokine-modulatory (CKM) regimen, combining rintatolimod (TLR3 agonist), interferon (IFN)-α2b and celecoxib (COX-2 inhibitor), selectively induces CTL-attractants but decreases MDSC- and Treg-attractants in the tumor microenvironment (TME). We hypothesized that the combination of CKM with paclitaxel will promote selective CTL infiltration into TNBC, and along with doxorubicin/cyclophosphamide (AC), will result in higher rate of pCR, translating into improved RFS and OS. METHODS: In the phase I study NCT04081389, 9 pts with stage I-III TNBC were enrolled with median age of 47 (37-55) years. All patients were treated with paclitaxel 80 mg/m2 IV weekly for 12 weeks, and for first 3 weeks days 1-3 also received CKM regimen consisting of rintatolimod 200 mg IV and celecoxib 200 mg oral twice daily. IFN-α2b was administered in an accelerated titration design at doses 0 or 5 million units (MU)/m2 [Dose Level (DL) 1,2 respectively] in first 2 pts (no intra-patient dose escalation), then 10 MU/m2 [DL 3] in 4 patients and then 20 MU/m2 [DL 4] in 3 patients. Pre- and 3 week-on treatment biopsies were performed at DL 3 and DL 4 (5 patients). This was followed by standard dose-dense AC and surgery. Dose-limiting toxicity (DLT) was defined as grade 3 or higher toxicity within the first 3 weeks of treatment. The primary endpoint was safety and tolerability, to determine the recommended phase II dose (RP2D) of CKM for extended efficacy study. The secondary endpoints included the efficacy (pCR), along with RFS and OS. Tumor and blood biomarkers were analyzed in exploratory studies. RESULTS: Treatment was well-tolerated with mostly grade 1 or 2 treatment-related adverse events (TRAEs) and no DLTs. Grade 3 TRAE were neutropenia (3/9), attributed to CKM (1/9) or paclitaxel (3/9), pneumonia (1/9) and anemia (1/9) attributed to AC. Two additional severe adverse events (pneumonia and squamous cell carcinoma of skin in situ) were observed, unrelated to study treatment. Paclitaxel- or AC-related toxicities were not higher than expected. There was no evidence of delayed or immune-related toxicities 90 days post-treatment. 5/9 (56%) pts attained pCR, and 1 additional pt had ypTmic at the time of surgery. There were no patients with progressive disease. All patients were able to get planned surgery with no additional delays observed. There was consistent (p=0.07) selective increase in CD8α (CTL marker) in on-treatment tumor biopsies with concomitant decrease in CD8α in the blood (p=0.04). CONCLUSIONS: The treatment was well-tolerated and no DLTs were observed and we determined RP2D for future studies. We observed promising clinical activity with pCR + ypTmic rate of 66%, comparable to pembrolizumab combination with NAC. A larger phase II study is being designed to confirm the observed efficacy and to determine if CKM regimen would be a safer short-term alternative to pembrolizumab or if CKM can overcome the resistance to the standard pembrolizumab/NAC therapy.

Citation Format: Shipra Gandhi, Mateusz Opyrchal, Cayla Ford, Ronald Slomba, Kristopher Attwood, Tracey O’Connor, Ellis Levine, Pawel Kalinski. Preliminary indications of safety and efficacy of neoadjuvant chemotherapy plus chemokine-modulating regimen (rintatolimod, IFN-α2b, celecoxib) in 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 P4-06-07.

Abstract P3-06-07: Phase Ib/II study to evaluate safety and tolerability of cabiralizumab in combination with nivolumab and neoadjuvant chemotherapy in patients with localized triple-negative breast cancer

Background: Neoadjuvant immune checkpoint inhibition (ICI) in combination with chemotherapy is approved for patients with high-risk, early-stage triple-negative breast cancer (TNBC) based on improved outcomes in the KEYNOTE-522 trial. However, some patients have primary resistant disease and do not achieve a pathological complete response (pCR), while others experience significant toxicity. Tumor-associated macrophages (TAMs) are a potential resistance mechanism for ICIs and are dependent on colony-stimulating factor 1 receptor (CSF1R). Therefore, we examined the addition of cabiralizumab, a CSF1R inhibitor, to neoadjuvant paclitaxel, carboplatin, and nivolumab to assess the safety, tolerability, and changes in the tumor microenvironment (TME) in patients with early-stage TNBC. Methods: This is a phase Ib/II, single-institution, randomized controlled clinical trial (NCT04331067) in patients with newly diagnosed Stage II-III TNBC. The primary endpoints include: (1) to determine the safety of a 12-week neoadjuvant regimen of paclitaxel (80 mg/m2 IV q week) + carboplatin (AUC5 IV q3 weeks) + nivolumab (240 mg IV q2 weeks) with or without cabiralizumab (4 mg/kg IV q2 weeks) and (2) to evaluate the effect of cabiralizumab on TAMs and changes in tumor infiltrating lymphocytes (TILs) in the TME between baseline and an on-treatment biopsy after 4 weeks of therapy. Adjuvant treatment is per investigator’s choice. Secondary objectives include evaluation of pCR rate and recurrence-free survival. Paired tissue and bone marrow biopsies are collected for evaluation of the TME and disseminated tumor cells, respectively. The study was designed to enroll 50 patients, including a 12-patient safety lead-in cohort. Here, we report the planned interim analysis of the safety lead-in cohort. Results: Between December 2020 and May 2022, we enrolled 12 patients to the safety lead-in, including 6 patients in each arm. 5 of 12 patients (41.7%) enrolled are underrepresented minorities, including 4 Black patients and 1 Hispanic patient. 2 of 6 patients in the nivolumab arm experienced grade 3 severe toxicity, including 1 patient who developed sepsis and 1 who developed peripheral neuropathy. 3 of 6 patients in the nivolumab + cabiralizumab arm developed grade 3 severe toxicity including 2 patients who experienced myositis and 1 patient who developed periorbital edema. Of the first 10 patients enrolled, 5 had a pCR (2 pCR in cabiralizumab arm, 3 pCR in non-cabiralizumab arm) and 3 had non-pCR (1 RCB-1 and 1 RCB-3 in cabiralizumab arm, 1 RCB-1 in non-cabiralizumab arm). 2 patients came off study prior to surgery (1 due to toxicity and 1 due to missing study visits). Data from the final 2 patients still on treatment will be available at the time of presentation. Discussion: Full safety, pathologic, and clinical response data in the safety lead-in cohort for patients with early-stage TNBC receiving neoadjuvant chemotherapy + nivolumab with or without cabiralizumab, will be presented.

Citation Format: Andrew A. Davis, Leonel Hernandez-Aya, Jingqin Luo, Mateusz Opyrchal, Foluso O. Ademuyiwa, Nusayba A. Bagegni, Katherine K. Clifton, Jill Anderson, Trish Hammerschmidt, Leslie Nehring, David DeNardo, Mark Watson, Rebecca Aft, Cynthia Ma, Katherine Weilbaecher. Phase Ib/II study to evaluate safety and tolerability of cabiralizumab in combination with nivolumab and neoadjuvant chemotherapy in patients with localized 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 P3-06-07.

A phase II study of palbociclib plus letrozole plus trastuzumab as neoadjuvant treatment for clinical stages II and III ER+ HER2+ breast cancer (PALTAN)

Patients with ER+/HER2+ breast cancer (BC) are less likely to achieve pathological complete response (pCR) after chemotherapy with dual HER2 blockade than ER-/HER2+ BC. Endocrine therapy plus trastuzumab is effective in advanced ER+/HER2+ BC. Inhibition of CDK4/6 and HER2 results in synergistic cell proliferation reduction. We combined palbociclib, letrozole, and trastuzumab (PLT) as a chemotherapy-sparing regimen. We evaluated neoadjuvant PLT in early ER+/HER2+ BC. Primary endpoint was pCR after 16 weeks. Research biopsies were performed for whole exome and RNA sequencing, PAM50 subtyping, and Ki67 assessment for complete cell cycle arrest (CCCA: Ki67 ≤ 2.7%). After 26 patients, accrual stopped due to futility. pCR (residual cancer burden-RCB 0) was 7.7%, RCB 0/I was 38.5%. Grade (G) 3/4 treatment-emergent adverse events occurred in 19. Among these, G3/4 neutropenia was 50%, hypertension 26.9%, and leucopenia 7.7%. Analysis indicated CCCA in 85% at C1 day 15 (C1D15), compared to 27% at surgery after palbociclib was discontinued. Baseline PAM50 subtyping identified 31.2% HER2-E, 43.8% Luminal B, and 25% Luminal A. 161 genes were differentially expressed comparing C1D15 to baseline. MKI67, TK1, CCNB1, AURKB, and PLK1 were among the genes downregulated, consistent with CCCA at C1D15. Molecular Signatures Database gene-sets analyses demonstrated downregulated processes involved in proliferation, ER and mTORC1 signaling, and DNA damage repair at C1D15, consistent with the study drug's mechanisms of action. Neoadjuvant PLT showed a pCR of 7.7% and an RCB 0/I rate of 38.5%. RNA sequencing and Ki67 data indicated potent anti-proliferative effects of study treatments. ClinicalTrials.gov- NCT02907918.

Inhibiting the biogenesis of myeloid-derived suppressor cells enhances immunotherapy efficacy against mammary tumor progression

While immune checkpoint inhibitors (ICIs) have transformed the therapeutic landscape in oncology, they are effective in select subsets of patients. Efficacy may be limited by tumor-driven immune suppression, of which 1 key mechanism is the development of myeloid-derived suppressor cells (MDSCs). A fundamental gap in MDSC therapeutics is the lack of approaches that target MDSC biogenesis. We hypothesized that targeting MDSC biogenesis would mitigate MDSC burden and bolster tumor responses to ICIs. We tested a class of agents, dihydroorotate dehydrogenase (DHODH) inhibitors, that have been previously shown to restore the terminal differentiation of leukemic myeloid progenitors. DHODH inhibitors have demonstrated preclinical safety and are under clinical study for hematologic malignancies. Using mouse models of mammary cancer that elicit robust MDSC responses, we demonstrated that the DHODH inhibitor brequinar (a) suppressed MDSC production from early-stage myeloid progenitors, which was accompanied by enhanced myeloid maturation; (b) augmented the antitumor and antimetastatic activities of programmed cell death 1-based (PD-1-based) ICI therapy in ICI-resistant mammary cancer models; and (c) acted in concert with PD-1 blockade through modulation of MDSC and CD8+ T cell responses. Moreover, brequinar facilitated myeloid maturation and inhibited immune-suppressive features in human bone marrow culture systems. These findings advance the concept of MDSC differentiation therapy in immuno-oncology.

Harnessing tumorous flaws for immune supremacy: is miRNA-155 the weak link in breast cancer progression?

With the advent of immune checkpoint blockade (ICB) therapy, treatment strategies for late-stage cancers have seen a radical advancement. In this issue of the JCI, Wang et al. characterize the functional role of miR-155 in breast cancer and its potential in harnessing the efficacy of immunotherapy. The study reports that high expression levels of miR-155 in breast cancer cells downregulated suppressor of cytokine signaling 1 (SOCS1), increased the phosphorylated STAT1 (pSTAT1)/pSTAT3 ratio, and thereby stimulated chemoattractants for tumor infiltration of effector T cells. Moreover, miR-155 overexpression set the stage for ICB therapy via increased programmed death ligand 1 (PD-L1) expression on cancer cells and enhanced immunological memory response via the release of miR-155–containing extracellular vesicles. Collectively, these data suggest that miR-155 is a strong candidate as a prognostic biomarker for ICB therapy.

Targeting PIM2 by JP11646 results in significant antitumor effects in solid tumors

Proviral integration of Moloney virus 2 (PIM2) is a pro-survival factor of cancer cells and a possible therapeutic target in hematological malignancies. However, the attempts at inhibiting PIM2 have yielded underwhelming results in early clinical trials on hematological malignancies. Recently, a novel pan-PIM inhibitor, JP11646, was developed. The present study examined the utility of targeting PIM2 in multiple solid cancers and investigated the antitumor efficacy and the mechanisms of action of JP11646. When PIM2 expression was compared between normal and cancer tissues in publicly available datasets, PIM2 was found to be overexpressed in several types of solid cancers. PIM2 ectopic overexpression promoted tumor growth in in vivo xenograft breast cancer mouse models. The pan-PIM inhibitor, JP11646, suppressed in vitro cancer cell proliferation in a concentration-dependent manner in multiple types of cancers; a similar result was observed with siRNA-mediated PIM2 knockdown, as well as an increased in cell apoptosis. By contrast, another pan-PIM inhibitor, AZD1208, suppressed the expression of downstream PIM2 targets, but not PIM2 protein expression, corresponding to no apoptosis induction. As a mechanism of PIM2 protein degradation, it was found that the proteasome inhibitor, bortezomib, reversed the apoptosis induced by JP11646, suggesting that PIM2 degradation by JP11646 is proteasome-dependent. JP11646 exhibited significant anticancer efficacy with minimal toxicities at the examined doses and schedules in multiple in vivo mice xenograft solid cancer models. On the whole, the present study demonstrates that PIM2 promotes cancer progression in solid tumors. JP11646 induces apoptosis at least partly by PIM2 protein degradation and suppresses cancer cell proliferation in vitro and in vivo. JP11646 may thus be a possible treatment strategy for multiple types of solid cancers.

Augmenting antibody response to EGF-depleting immunotherapy: Findings from a phase I trial of CIMAvax-EGF in combination with nivolumab in advanced stage NSCLC

Background

CIMAvax-EGF is an epidermal growth factor (EGF)-depleting immunotherapy which has shown survival benefit as a switch maintenance treatment after platinum-based chemotherapy in advanced non-small cell lung cancer (NSCLC). The primary objective of this trial is to establish the safety and recommended phase II dose (RP2D) of CIMAvax-EGF in combination with nivolumab as second-line therapy for NSCLC.

Methods

Patients with immune checkpoint inhibitor-naive metastatic NSCLC were enrolled using a “3+3” dose-escalation design. Toxicities were graded according to CTCAE V4.03. Thirteen patients (one unevaluable), the majority with PD-L1 0%, were enrolled into two dose levels of CIMAvax-EGF.

Findings

The combination was determined to be safe and tolerable. The recommended phase 2 dose of CIMAvax-EGF was 2.4 mg. Humoral response to CIMAvax-EGF was achieved earlier and in a greater number of patients with the combination compared to historical control. Four out of 12 evaluable patients had an objective response.

A dose regimen-finding study to evaluate the safety, tolerability, pharmacokinetics, and activity of oratecan in subjects with advanced malignancies

PURPOSE

Irinotecan is a commonly used chemotherapeutic in solid tumor malignancies. Oratecan is an investigational product comprised of encequidar methanesulfonate, a novel minimally absorbed P-glycoprotein pump inhibitor, and irinotecan. This study sought to determine the maximum tolerated dose (MTD) of oratecan in patients with advanced malignancies.

METHODS

Using a "3 + 3″ dose-escalation design, patients were treated with oratecan on day 1 every 21 days. The irinotecan dose was escalated from 20 to 320 mg/m². The encequidar methanesulfonate dose was fixed at 15 mg (12.9 mg free base). PK sampling for irinotecan, encequidar and its major metabolites was performed following a single dose of oratecan during cycle 1. Patients were treated until disease progression or unacceptable toxicity.

RESULTS

Thirty-five patients were treated. The MTD was determined to be 280 mg/m² every 21 days. Irinotecan and SN-38 plasma concentration-time profile showed that irinotecan exposure increased with dose and followed biexponential decay. Nine of 17 patients at oratecan dose levels 200 mg/m² and above had SN-38 exposures comparable to those with intravenous irinotecan at standard dosing. None of the 35 patients achieved a radiologic response, ten patients had SD for > 8 weeks; the median progression-free survival for all treated patients was 9 weeks (95% CI 8.6-13.9).

CONCLUSIONS

The MTD of oratecan was encequidar methanesulfonate 15 mg plus irinotecan 280 mg/m². Exposure for irinotecan and SN-38 increased with increased dose. Potential antitumor activity was observed at the 280 and 320 mg/m² dose levels. The safety profile of oratecan was comparable to that of intravenous irinotecan.

Abstract CT145: Systemic rintatolimod and interferon-α2b selectively reprogram local tumor microenvironment in patients with metastatic triple negative breast cancer for enhanced influx of cytotoxic T-lymphocytes but not regulatory T-cells

Background: Effective immune therapies depend on the presence of cytotoxic T-lymphocytes (CTLs) in the tumor microenvironment (TME). Our preclinical data showed synergy between TLR3 ligands and interferon-α (IFN-α) in reprogramming the TME, but not healthy tissues, to selectively enhance CTL attraction, providing rationale for their systemic application to enhance local CTL densities in “cold” tumors. The pilot study NCT03599453 evaluated the safety of systemic chemokine modulating regimen (CKM) composed of i.v. rintatolimod (Ampligen; selective TLR3 ligand) and IFN-α, and its ability to promote local CTL influx to mTNBC lesions.

Methods: Six evaluable patients (33-75 years) with mTNBC received 6 doses of rintatolimod (200 mg i.v.), IFN-α (INTRON-A; 20MU/m2 i.v.) and COX-2 inhibitor (celecoxib; 2 x 200 mg, p.o.) over 2 weeks, with tumor biopsies obtained before (within 6 days) and after (within 5 days) CKM. All patients received follow-up pembrolizumab (200 mg, i.v, Q3 weeks). The primary endpoint was the change in the CTL marker CD8α in the TME with a planned interim analysis after 3 patients (α=0.03) and final analysis after 6 patients (α=0.084). Correlative studies analyzed additional markers of CTLs, regulatory T-cells (Tregs), and CTL- and Treg-attracting chemokines in the TME and blood.

Results: Treatment was well tolerated with mostly grade 1/2 adverse events and one grade 3 clinically significant pneumonitis and immune thrombocytopenic purpura observed during follow up pembrolizumab treatment. We observed uniform increases of intratumoral type-1 immune markers upon treatment: CD8α mRNA (6.1-fold; p=0.034), GZMB (3.5-fold; p=0.058), ratios of CD8α/FOXP3 and GZMB/FOXP3 (5.7-fold; p=0.036, and 7.6-fold; p=0.024 respectively), and CTL attractants CXCL10 (2.6-fold; p=0.104) and CCL5 (3.3-fold; p=0.019), successfully meeting the primary endpoint. In contrast, neither Treg marker Foxp3 nor Treg attractants CCL22 or CXCL12 were enhanced. These TME changes were accompanied by transient decreases in circulating CD3+CD8+ CTLs and CD3-CD56+ NK cells (but not Tregs), selectively affecting the cells expressing CXCR3 (receptor for CXCL10), but not CCR4 or CXCR4 (receptors for CCL22 and CXCL12). Three patients had stable disease lasting 2.4, 2.5 and 3.8 months, as of September 1, 2021 cut-off. An additional patient had a partial response (breast auto-amputation) with massive tumor necrosis observed in the post-CKM biopsy.

Conclusion: This proof-of-concept study shows that short-term systemic CKM followed by pembrolizumab is safe and selectively enhances local CTL infiltration in the TME, providing rationale for concurrent CKM and PD1 blockade in prospective phase II studies.

Citation Format: Shipra Gandhi, Mateusz Opyrchal, Melissa Grimm, Ronald Slomba, Kathleen Kokolus, Sebastiano Battaglia, Kristopher Attwood, Adrienne Groman, Lauren Williams, Mary Lynne Tarquini, Paul Wallace, Kah Teong Soh, Tracey O'Connor, Amy Early, Ellis Levine, Igor Puzanov, Marc Ernstoff, Pawel Kalinski. Systemic rintatolimod and interferon-α2b selectively reprogram local tumor microenvironment in patients with metastatic triple negative breast cancer for enhanced influx of cytotoxic T-lymphocytes but not regulatory T-cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT145.

Rationale and design of phase 1 FTIH study of FOXP3 antisense oligonucleotide AZD8701 in patients with selected advanced solid tumors

TPS3166

Background: The forkhead box family transcription factor FOXP3 is essential for T regulatory cells (Tregs) development and immune suppressive function. Tregs are an integral component of the adaptive immune system and contribute to maintaining tolerance to self-antigens and preventing autoimmune diseases. In the context of cancer, however, Tregs contribute to tumor progression by suppressing antitumor immunity. To date inhibition of Treg-mediated immunosuppression tested in the clinic has lacked specificity. Targeting FOXP3 provides a selective approach to impair the immunosuppressive function of Tregs but targeting transcription factors has been a challenge using conventional drug modalities. AZD8701 employs next-generation antisense oligonucleotide (ASO) technology (Ionis Pharmaceuticals) to bind mRNA with high affinity and selectively reduce human Foxp3 mRNA expression levels. Foxp3-specific ASOs promote potent dose-dependent reductions in Foxp3 mRNA and protein in vitro. In preclinical models, AZD8701 induced Foxp3 knockdown results in Tregs with a reduced immunosuppressive capacity, loss of immunosuppressive markers, and increased markers of activation on CD8+ T-cells. AZD8701 reduces tumor growth as monotherapy in preclinical models and increased tumor inhibition is obtained by combining AZD8701 with a PD-L1 inhibitor. Methods: This is a Phase I multicenter study of AZD8701 alone or in combination with durvalumab in participants with selected advanced solid tumors. Eligible patients must have ECOG performance status 0 or 1, measurable target lesion per RECIST v1.1 and be diagnosed with selected tumor types as described below. Monotherapy and combination dose escalation phase is open for participants with head and neck squamous cell carcinoma (HNSCC), triple-negative breast cancer (TNBC), non-small-cell lung cancer (NSCLC), clear cell renal cell carcinoma (ccRCC), gastroesophageal cancer, melanoma, cervical cancer, small-cell lung cancer (SCLC), and/or solid tumors that have demonstrated a response to prior programmed death-ligand-1 (PD-[L]1) treatment (as defined by duration of response > 18 weeks). Participants with NSCLC, HNSCC, TNBC, and ccRCC will be included in the pharmacodynamic cohort at the selected monotherapy dose and/or disease expansion cohorts. The primary objectives are to assess safety and tolerability and to determine the preliminary antitumor activity of AZD8701 (objective response rate) when administered as monotherapy or in combination with durvalumab. Secondary endpoints include, disease control rate, duration of response, progression free survival and overall survival, pharmacokinetics and pharmacodynamics (including changes in Foxp3 mRNA in paired tumor samples). The trial is currently recruiting. Clinical trial information: NCT04504669.

Systemic Therapy De-Escalation in Early-Stage Triple-Negative Breast Cancer: Dawn of a New Era?

Simple Summary

Triple-negative breast cancer is a life-threatening disease, even when identified at early stages. Recent advances have allowed the improvement of life expectancy via a personalized approach with the addition of newer chemotherapies, immunotherapies, and targeted therapies, but at the cost of added side effects. It has become increasingly clear that not all patients need such aggressive treatment. Here, we provide an overview of emerging opportunities to use less toxic therapies in patients at lower risk of recurrence or with mutations that can be effectively targeted using novel approaches. We provide a comprehensive review of completed and ongoing clinical trials with information on how to best stratify these patients for treatments to obtain maximum benefit without unnecessary toxicities.

Abstract

Early-stage triple negative breast cancer (TNBC) has been traditionally treated with surgery, radiation, and chemotherapy. The current standard of care systemic treatment of early-stage II and III TNBC involves the use of anthracycline-cyclophosphamide and carboplatin-paclitaxel with pembrolizumab in the neoadjuvant setting followed by adjuvant pembrolizumab per KEYNOTE-522. It is increasingly clear that not all patients with early-stage TNBC need this intensive treatment, thus paving the way for exploring opportunities for regimen de-escalation in selected subgroups. For T1a tumors (≤5 mm), chemotherapy is not used, and for tumors 6–10 mm (T1b) in size with negative lymph nodes, retrospective studies have failed to show a significant benefit with chemotherapy. In low-risk patients, anthracycline-free chemotherapy may be as effective as conventional therapy, as shown in some studies where replacing anthracyclines with carboplatin has shown non-inferior results for pathological complete response (pCR), which may form the backbone of future combination therapies. Recent advances in our understanding of TNBC heterogeneity, mutations, and surrogate markers of response such as pCR have enabled the development of multiple treatment options in the (neo)adjuvant setting in order to de-escalate treatment. These de-escalation studies based on tumor mutational status, such as using Poly ADP-ribose polymerase inhibitors (PARPi) in patients with BRCA mutations, and new immunotherapies such as PD1 blockade, have shown a promising impact on pCR. In addition, the investigational use of (bio)markers, such as high levels of tumor-infiltrating lymphocytes (TILs), low levels of tumor-associated macrophages (TAMs), and complete remission on imaging, also look promising. In this review, we cover the current standard of care systemic treatment of early TNBC and review the opportunities for treatment de-escalation based on clinical risk factors, biomarkers, mutational status, and molecular subtype.

Abstract P5-13-20: Identifying a metabolite signature that correlates with tumor proliferation in early-stage breast cancer patients treated with CDK4/6 inhibitors from matched plasma and serum samples

Background: Cyclin-dependent kinase 4/6 inhibitors (CKD4/6i) have demonstrated clinical utility extending progression-free survival (PFS) and overall survival (OS) for advanced hormone receptor positive and HER2 negative (HR+/HER2-) breast cancer patients. The efficacy in early-stage breast cancer (eBC) is unclear, with conflicting results from adjuvant CDK4/6i trials on invasive disease-free survival. Thus, there is a critical need to identify biomarkers of response (BoR) to determine which, if any, eBC patients could benefit from this treatment. This BoR could also stratify advanced BC patients for likelihood to respond to CDK4/6i. Metabolism is influenced by both genome and environment, and changes in the metabolome can be correlated with drug responsiveness. Thus, metabolite BoRs may serve to identify eBC patients for which CDK4/6i would offer a therapeutic benefit.Methods: Plasma and serum samples from 50 early-stage ER+/HER2- breast cancer patients, treated with neoadjuvant CDK4/6 inhibitor palbociclib (palbo) and aromatase inhibitor (AI) anastrozole on NeoPalAna trial (ClinicalTrials.gov identifier NCT01723774), were collected from treatment-naïve patients (BL) and 3 consecutive time points: anastrozole,1 mg daily for 4 weeks (C1D1), anastrozole plus palbo,125 mg daily, for 15 days (C1D15), and for 4-5 months before surgery (SURG). Metabolites were extracted from all samples via methanol and chloroform precipitation and quantified using an unbiased, non-destructive, nuclear magnetic resonance (NMR)-based profiling platform (Olaris®, Inc., Waltham, MA). Statistical analysis and machine learning was used to identify differential metabolites and generate predictive models. A separate validation set of samples was collected from a subset of patients (N=6) who received an additional cycle of palbo treatment prior to surgery to assess model accuracy. Results: Non-parametric differential expression analysis of BL/C1D1, BL/C1D15, and C1D1/C1D15 identified 53 ,97, and 90 differential NMR resonances in plasma (p&lt;0.05) and 36, 34, and 25 differential NMR resonances in serum (p&lt;0.05), respectively. Based on the proliferative marker Ki67 levels at C1D15, 37 patients were classified as responders (Ki67≤2.7%) and 6 patients as non-responders (Ki67&gt;2.7%). Analysis of the responder (R) and non-responder (NR) groups identified that 13 plasma and 14 serum resonances (21 unique resonances and 6 overlapping) were differentially expressed (p&lt;0.05) at C1D1. Many of the differential resonances could be mapped back to amino acid metabolites including several branched chain amino acids such as leucine, valine, and isoleucine, and positively charged amino acids such as lysine. A Olaris® BoR score was generated using 5 differential resonances that had an AUC of 0.931 (training set) and 100% accuracy when predicting palbo-response in a blinded test set (N=6).Conclusion: The differential metabolites identified from matching plasma and serum samples suggest that, compared to serum, plasma has a better representation of the metabolic changes associated with palbo treatment-response. While comparing samples from R and NR patients, amino acids were found to be consistently altered in both serum and plasma before palbo treatment. In addition, a BoR model based on select metabolites could precisely stratify palbo-response in a blinded dataset. A larger independent validation cohort is ongoing.

Citation Format: Chen Dong, Shana Thomas, Chandrashekhar Honrao, Leonardo O. Rodrigues, Nathalie Tessier, Bo Zhang, Souzan Sanati, Kiran Vij, Brenda J. Ernst, Karen S. Anderson, Mateusz Opyrchal, Foluso Ademuyiwa, Lindsay L. Peterson, Matthew P. Goetz, Donald Northfelt, Elizabeth O'Day, Cynthia Ma. Identifying a metabolite signature that correlates with tumor proliferation in early-stage breast cancer patients treated with CDK4/6 inhibitors from matched plasma and serum samples [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 P5-13-20.

Abstract PD14-04: Circulating tumor DNA characterization of invasive lobular carcinoma in patients with metastatic breast cancer

Background:Invasive lobular carcinoma (ILC) is the second most common histology of breast cancer, accounting for approximately 10-15% of cases. Prior studies have demonstrated that loss of E-cadherin, as well as alterations in tissue including CDH1, FOXA1, TBX3 and PTEN loss, that were more commonly observed in Luminal A ILC, while GATA3 was more commonly observed in invasive ductal carcinoma (IDC) (Ciriello et al., Cell 2015). However, data regarding the characterization of circulating tumor DNA (ctDNA) in patients (pts) with metastatic ILC are limited. We hypothesized that there would be distinct mutational profiles between pts with metastatic ILC and IDC that could be characterized using ctDNA. Methods:This retrospective cohort study included de-identified clinical, pathological, and ctDNA data from pts with metastatic breast cancer (MBC) combined under a data use agreement and approved by the institutional review boards of three sites: Washington University in St. Louis (MO), Northwestern University (Chicago, IL), and Massachusetts General Hospital (Boston, MA). All pts included in the study had ctDNA testing per standard of care with plasma-based genotyping performed by Guardant360 (Redwood City, CA) between 2015-2020. Histological classification (ILC vs. IDC) was defined based on review of pathology reports from the primary tumor or from breast biopsies of de novo MBC, and additional clinical and pathological variables were obtained via electronic medical record review. Single nucleotide variants (SNVs) were annotated using OncoKB and ClinVar and only pathogenic variants were included. Mutational profiles were compared across histologic subtypes using Fisher’s exact test to assess differences in alteration frequency across subtypes. Multivariable analysis was performed. Results:A total of 994 pts with MBC underwent ctDNA testing and were included in the analysis. 10.7% of pts had ILC (N=106) and 89.3% had IDC (N=888). 89.4% of ILC cases were categorized as hormone-receptor positive (HR+) compared with 67.1% of IDC cases. Pts with ILC had a lower frequency of triple-negative (6.7% vs. 17.7%) and HER2 positive (3.9% vs. 15.2%) breast cancer compared with IDC. Pts with ILC had a significantly higher number of pathogenic SNVs compared with IDC (mean 4.45 vs. 2.77; P=0.0037). In contrast, pts with ILC had a significantly lower number of copy number alterations as compared to pts with IDC (mean 0.40 vs. 1.03; P=0.0017). No differences were observed in mutant allele frequency between pts with ILC and IDC. The 5 most common alterations observed in pts with ILC were the following: PIK3CA, TP53, ESR1, ERBB2, and ARID1A. Alterations in AR, BRAF, CDH1, ERBB2, FGFR2, IDH2, KRAS, NF1, PIK3CA, SMAD4, and TERT were significantly higher in ILC than IDC (all P&lt;0.05). In contrast, mutations in GATA3, and amplifications in ERBB2 and MYC were significantly more common in pts with IDC (all P&lt;0.05). In multivariable analysis, mutations in BRAF, CDH1, ERBB2, IDH2, TERT remained significantly higher in ILC, while amplification of MYC was significantly higher in IDC (all P&lt;0.05). After restricting the analysis to pts with HR+ HER2 negative MBC, the following genes were significant in multivariate analysis: CDH1 and ERBB2 for pts with ILC and MYC amplification for pts with IDC (all P&lt;0.05). Discussion:In this large, multi-institutional dataset, pts with metastatic ILC were characterized by a significantly higher number of SNVs in ctDNA compared to pts with IDC, suggesting higher mutational burden. We report several alterations that were significantly different in ILC vs. IDC. These results demonstrate the ctDNA profile of pts with ILC, and future studies should explore serial plasma-based genotyping to track ILC evolution to develop targeted precision medicine based therapeutic approaches for this unique subset of pts with MBC.

Citation Format: Andrew A Davis, Lorenzo Gerratana, Katherine Clifton, Marko Velimirovic, Whitney L Hensing, Ami N Shah, Paolo D’Amico, Carolina Reduzzi, Qiang Zhang, Charles S Dai, Elyssa N Denault, Nusayba A Bagegni, Mateusz Opyrchal, Foluso O Ademuyiwa, Ron Bose, William J Gradishar, Amir Behdad, Cynthia X Ma, Aditya Bardia, Massimo Cristofanilli. Circulating tumor DNA characterization of invasive lobular carcinoma in patients with metastatic 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 PD14-04.

Abstract P2-01-01: Genetic alterations detected by circulating tumor DNA (ctDNA) in HER2-low metastatic breast cancer (MBC)

Introduction: Approximately 40-50% of breast cancers are characterized by low HER2 expression (HER2-low), defined as immunohistochemistry (IHC) 1+ or 2+ and HER2 fluorescence in situ hybridization (FISH) unamplified, encompassing a large and heterogeneous subgroup that may confer benefit from novel HER2 directed therapies. Circulating tumor DNA (ctDNA) has emerged as a minimally invasive technique to detect cancer-specific gene aberrations. Genetic alterations in ctDNA of HER2-low MBC have not been well described, and we hypothesized that HER2-low MBC may have a distinct genomic profile, beyond standard histopathologic features. Methods: This retrospective cohort study included patients with MBC treated at Washington University in St. Louis, Northwestern University (Chicago, IL) and Massachusetts General Hospital (Boston, MA) who had undergone ctDNA analysis during the course of treatment using the commercially available Guardant360® assay. HER2 expression was evaluated by IHC/FISH according to ASCO/CAP guidelines on metastatic tissue biopsies (or primary breast tumor tissue if a metastatic site biopsy was not available). Tumors were classified as HER2-low (IHC 1+ or 2+/FISH negative), HER2-0 (IHC 0) or HER2-positive (IHC 3+ or IHC 2+/FISH amplified). Clinicopathologic characteristics and ctDNA genetic alterations for HER2-low MBC were described and compared with the HER2-0 and HER2-positive subgroups. Chi-square and Fisher’s exact tests were used for categorical variables. Logistical regression was performed for multivariable analyses. Results: A total of 991 patients with MBC were analyzed, including 160 (16.1%) HER2-positive, 351 (35.4%) HER2-0, and 480 (48.4%) HER2-low MBC. The majority (89.2%) of HER2-low MBC were estrogen-receptor positive (ER+). Compared with HER2-0 MBC, HER2-low MBC had a significantly higher incidence of PIK3CA mutations (OR 1.54, p=0.027). PDGFRA and MYC amplifications were also more common among HER2-low MBC (2.3% vs 0.28% and 8.1% vs 4.6%, respectively), although not significantly associated with this subtype in multivariable analysis. Within the ER+ MBC cohort, those with HER2-low also had higher rates of PIK3CA mutations (OR 1.66, p=0.012) and MYC amplification (OR 2.29, p=0.034), as compared to HER2-0. Compared with HER2-positive, HER2-low MBC had significantly lower rates of ERBB2 alterations (OR 0.26, p=0.0076 for ERBB2 mutations and OR 0.022, p&lt;0.001 for ERBB2 amplification). ESR1, AKT1, and RB1 mutations were more common in HER2-low compared with HER2-positive MBC (14.0% vs 6.9%; 3.1% vs none; 3.1% vs none, respectively), but were not significant in multivariable analysis. Conclusions: Among patients with ER+ MBC, HER-low had a higher incidence of PIK3CA mutations and MYC amplification compared to HER2-0 MBC, and both of these alterations have been implicated as mechanisms of endocrine resistance. We did not demonstrate a high incidence of ERBB2 alterations in patients with HER2-low MBC. To our knowledge, this is the first study to describe genetic alterations detected by ctDNA in patients with HER2-low MBC. Given the emergence of novel HER2-targeted antibody drug conjugates with clinical activity in HER2-low MBC, these findings may guide combination treatment strategies and patient selection for future studies. Further studies are needed to confirm whether HER2-low MBC represents a truly unique biologic subtype.

Citation Format: Whitney L Hensing, Lorenzo Gerratana, Katherine Clifton, Marko Velimirovic, Ami Shah, Paolo D'Amico, Carolina Reduzzi, Qiang Zhang, Charles S Dai, Nusayba A Bagegni, Mateusz Opyrchal, Foluso O Ademuyiwa, Bose Ron, Amir Behdad, Cynthia X Ma, Aditya Bardia, Massimo Cristofanilli, Andrew A Davis. Genetic alterations detected by circulating tumor DNA (ctDNA) in HER2-low metastatic breast cancer (MBC) [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 P2-01-01.

Abstract P2-13-01: Phase 2 study of neoadjuvant palbociclib, letrozole, and trastuzumab in patients with ER+ HER2+ breast cancer (PALTAN)

Background Patients (pts) with ER+ HER2+ breast cancer (BC) are less likely to achieve pathological complete response (pCR) after neoadjuvant chemotherapy with dual HER2 blockade than pts with ER- HER2+ BC. Endocrine therapy (ET) plus trastuzumab is effective in advanced ER+ HER2+ BC, but pCR rate is low in the neoadjuvant setting. Inhibition of CDK4/6 and HER2 results in synergistic reduction in cell proliferation in preclinical studies. We therefore combined ET with CDK4/6 inhibition and trastuzumab in ER+ HER2+ BC as a chemotherapy-sparing regimen. Methods We evaluated the efficacy of palbociclib, letrozole, trastuzumab (PLT) in the neoadjuvant setting for pts with stages II or III ER+ HER2+ BC. Primary endpoint was pCR after 16 weeks of therapy. We assumed null of 15% pCR and pCR ≥ 30% warrants further investigation. To achieve 80% power at 1-sided 0.05 significance, 48 pts were to be enrolled. Evaluable population included pts who completed Cycle (C) 1 unless discontinued due to treatment-emergent adverse events (TEAEs) prior to completing C1. All who received one dose on study were considered evaluable for toxicity. Biopsies were collected at baseline (BL), C1 day 15 (C1D15), and surgery for RNA sequencing and central Ki67 assessment, for PAM50 subtype distribution, complete cell cycle arrest (CCCA: Ki67 ≤2.7%) at C1D15 and surgery, and treatment induced signaling changes. Results Accrual stopped early due to futility. 26 pts accrued were evaluable for efficacy and toxicity. pCR (residual cancer burden- [RCB] 0) was 7.7% (95% CI 0.9 - 25.1%) and RCB 0/I was 38.5% (95% CI 20.2 - 59.4%). TEAEs (n= 337) were seen in all pts (71.5% grade [G] 1, 19.3% G2, 8.6% G3, 0.6% G4); the most common were leukopenia (7.7%), neutropenia (7.1%), anemia (5.9%). G3/4 TEAEs occurred in 19 pts (73.1%). Among the 19, incidence of G3/4 neutropenia was 50%, hypertension 26.9%, leucopenia 7.7%. TEAEs (hypertension, ventricular tachycardia, pulmonary edema) leading to treatment discontinuation were reported in 1 pt. Two pts had at least one SAE. No treatment-related deaths occurred. Pt reported outcomes using NCI PRO-CTCAE revealed no differences in appetite, nausea, respiratory symptoms, edema, palpitations, rashes and dry skin, or concentration from BL to end of C4. Pts had worsening hair loss from BL to end of C4. Ki67 analysis indicated CCCA in 78% at C1D15, compared to 18% at surgery after only P had been discontinued approximately 4 weeks prior to surgery. RNA sequencing was performed on available biopsies collected at BL (N=16), C1D15 (N=5), and surgery (N=2) from 16 pts. Among 16 BL samples, PAM50 subtyping identified 5 (31.3%) basal-like, 2 (12.5%) HER2-E, 6 (37.5%) Lum B, and 3 (18.8%) normal. Subtype switching to Lum A at C1D15 (N=3, 1 each with HER2-E, Lum B, and normal at BL) or normal (N=2, 1 basal and 1 HER2-E at BL) was observed. 161 genes were differentially expressed (FDR p&lt;0.05); 145 downregulated and 16 upregulated comparing C1D15 to BL. MKI67, TK1, CCNB1, AURKB, PLK1 were among the downregulated genes, consistent with CCCA for majority of the samples at C1D15 by Ki67. Analysis of the Molecular Signatures Database Hallmark gene-sets comparing C1D15 and BL samples demonstrated downregulated biological processes involved in proliferation (E2F targets, G2M checkpoint, MYC targets, mitotic spindle), signaling (Estrogen response, mTORC1 signaling), and DNA damage (DNA repair) at C1D15, consistent with the mechanisms of action of the study drugs. E2F targets were higher in BL samples of RCB II/III, compared to RCB I (FDR p=0.042). Conclusions PALTAN did not meet its primary endpoint of pCR. Neoadjuvant PLT showed a pCR of 7.7% but was well tolerated. RNA sequencing and Ki67 data indicated potent anti-proliferative effects of study treatments, despite significant heterogeneity of intrinsic subtypes. Clinical trial information: NCT02907918.

Citation Format: Foluso O Ademuyiwa, Donald Northfelt, Tracey O'Connor, Ellis Levine, Jingqin Luo, Yu Tao, Jeremy Hoog, Marie Laury, Tracy Summa, Trish Hammerschmidt, Zhanfang Guo, Ashley Frith, Katherine Weilbaecher, Mateusz Opyrchal, Rebecca Aft, Katherine Clifton, Rama Suresh, Nusayba Bagegni, Ian S Hagemann, Cynthia X Ma. Phase 2 study of neoadjuvant palbociclib, letrozole, and trastuzumab in patients with ER+ HER2+ breast cancer (PALTAN) [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 P2-13-01.

Abstract P4-07-23: Piezo1 is associated with worse prognosis along with promoted epithelial-mesenchymal transition and hypoxia as well as less anti-cancer immune cells in hormone receptor (HR)-negative breast cancer

Introduction: Piezo1 is a transmembrane protein, forming a mechano-sensitive ion channel. Piezo channels play an important role in mechano-sensing and mechano-transduction. Stretch activation of Piezo channels lead to influx of cations and activation of additional Ca2+ channels and depolarization. There are early evidences that Piezo1 channel signaling alters cancer cell behavior. It promotes migration in breast cancer cells, migration and chemo-resistance in gastric cancer cells, invasion of osteosarcoma cells, and enhances cell survival in synovial sarcoma cells. Contrary, lower level of Piezo1 associates with more invasive phenotype in lung cancer. In this study, we aimed to investigate clinical relevance of Piezo1 expression in breast cancer. Methods: In order to investigate Piezo1 clinical relevance in breast cancer patients, we used The Cancer Genome Atlas (TCGA) breast cancer cohort as a testing cohort, and GSE3494 as validation cohort. Piezo1 expression levels were compared among different stages as well as breast cancer subtypes. Patients’ survival was compared based on Piezo1 expression in each subtype. Gene set enrichment analysis (GSEA) and cibersort algorithms were used to evaluate pathways and infiltrating immune cells associated with PIEZO1 expression. Results: There was no significant difference in PIEZO1 expressions based on AJCC stage (P=0.258). PIEZO1 expression was significantly higher in the hormone receptor (HR)-negative (both estrogen receptor (ER)- and progesterone receptor (PR)-negative) tumors (P&lt;0.001), whereas, there was no significant difference between HER2-positive and -negative tumors (P=0.279). When we compared patient survival based on PIEZO1 expression, there was no significant difference in the whole breast cancer cohort (disease-free survival (DFS); P=0.201, overall survival (OS); P=0.694). On the other hand, high PIEZO1 expression showed significantly worse prognosis for both DFS (P=0.033) and OS (P=0.002) in the HR-negative cohort, but not in HR-positive cohort (DFS; P=0.995, OS; P=0.083). These findings were validated in validation cohort GSE3494, in which PIEZO1 expression was higher in the HR-negative patients as compared to its counterpart (P=0.006) and higher PIEZO1 showed worse prognosis in the HR-negative cohort (P=0.003). As possible mechanisms, GSEA revealed that PIEZO1 high expression tumor was associated with cancer aggressiveness characteristics, such as epithelial-mesenchymal transition (EMT) (P&lt;0.001) and hypoxia (P&lt;0.001) in HR-negative breast cancer. Further, PIEZO1 high expressing tumor has less anti-cancer immune cells, including activated CD4+ memory T cells (P=0.020) and CD8+ T cells (P=0.002). Conclusion: We found that PIEZO1 high expression was associated with poor prognosis in HR-negative breast cancer patients. It may be due to promoted EMT and hypoxic condition, as well as less immunogenic characteristics.

Citation Format: Eriko Katsuta, Kazuaki Takabe, Mateusz Opyrchal. Piezo1 is associated with worse prognosis along with promoted epithelial-mesenchymal transition and hypoxia as well as less anti-cancer immune cells in hormone receptor (HR)-negative 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 P4-07-23.

Development of KAM score to predict metastasis and worse survival in breast cancer

Some may think that prediction of metastasis is meaningless since metastatic breast cancer is currently incurable. We argue that effective identification of developing metastasis will enable us to design and conduct clinical trials specifically targeting those patients at high risk. The current study sought to generate the KAM score by 4 genes (BRSK2, EYA1, SIGLEC15, and AGTR1) overexpressed in primary breast cancer that developed metastasis to bone compared with matched controls without metastasis longer than 10 years. A high KAM score was prognostic of poor overall (OS), disease free survival (DFS), and disease specific survival (DSS) in the METABRIC, and OS in the GSE96058 cohorts. A high KAM score was significantly associated with clinical aggressiveness, such as high American Joint Committee Cancer (AJCC) stage, lymph node metastasis, Nottingham pathological grade, and triple negative breast cancer (TNBC). Subgroup analysis revealed that a high KAM score was associated with worse OS in ER-positive/HER2-negative breast cancer in both cohorts. A high KAM breast cancer enriched all 5 cell proliferation-related gene sets of the Hallmark collection and interferon (IFN)-γ response gene sets. Furthermore, a high KAM breast cancer was significantly infiltrated with a high fraction of not only anti-cancer but also pro-cancer immune cells and associated with high level of cytolytic activity. Finally, a high KAM breast cancer was significantly associated with lung metastasis. In conclusion, we developed KAM score using 4 gene expressions that predict lung metastasis and patient survival in breast cancer.

337 Intratumoral immune therapy for recurrent breast cancer with polyICLC, and tremelimumab combined with systemic durvalumab

Background

Intratumoral (IT) cancer therapies may enhance T cell activation and tumor infiltration when combined with systemic checkpoint blockade. This approach may improve treatment of advanced breast cancer, which is commonly resistant to immune therapy.

Methods

A multicenter basket-style trial (NCT02643303) was performed in patients with advanced solid tumors, who received polyICLC IT 1mg x 6, then intramuscular (IM) x 3, combined with intravenous (IV) durvalumab 1500 mg q4W. Most were assigned to cohorts also receiving tremelimumab: 10 mg IT or 75 mg IV. Goals were to assess tolerability and clinical activity. Treated tumors were evaluated for immune infiltrates on days (d) 0, 15, and 29 by multiparameter immunofluorescence histology. A strong signal for clinical response was in breast cancer patients; thus, an expansion cohort was enrolled. We report analysis of that breast cancer subgroup.

Results

Nineteen participants with treatment-refractory recurrent breast cancer with median 4 prior lines of therapy were enrolled and treated with IV durvalumab and IT/IM polyICLC. Seventeen also received tremelimumab (15 IT, 2 IV). Common treatment-related AEs were fatigue, injection site pain, and chills. There was one dose-limiting toxicity in a participant who received tremelimumab IV, and died with severe hyponatremia (DLT) and progressive disease. Objective clinical responses (1 complete; 4 partial (1 unconfirmed)) were observed in 5 (26%), including 2/9 patients with triple-negative breast cancer (TNBC) and 3/10 with non-TNBC. Median OS was longer for those with CR, PR, or SD (not reached) vs. those with PD or not evaluable (5 months): two responders remain alive at 34+ and 40+ months. In injected tumors, there were significant increases from d0 to d29 in numbers/mm2 of CD8+ T cells, CD20+ B cells, mature dendritic cells (DC), macrophages, and CD56+ NK cells, and in CD8+ cells with antigen-experience (CD45RO), cytotoxic function (granzyme B), activation (ICOS1), or proliferation (Ki67). CD8+ cells expressing LAG3 and TIM3 increased, as did PDL1+ tumor cells and stromal cells. There were no differences in cells expressing IDO, ARG1, CD39, or CD73. Among patients with objective response, vs. all others, proportions of intratumoral CD8+ cells expressing Ki67 increased (p < 0.04).

Conclusions

IT tremelimumab and polyICLC plus systemic durvalumab is safe and has clinical activity in patients with advanced TNBC and non-TNBC. The therapy enhances intratumoral immune effectors and markers of T cell function in hypothesis-generating data that warrant confirmatory studies. Clinical response was associated with longer survival and increased CD8 T cell proliferation.

Trial Registration

NCT02643303

Ethics Approval

The study has been performed with approval of the institutional review boards of each participating institution (Roswell Park Cancer Institute: STUDY 00000121/I291016; Mount Sinai School of Medicine: IRB-17-01692; University of Virginia: IRB # 19276; Cleveland Clinic: 18-694; Toledo: 300176; Dartmouth: STUDY00031630; Emory: IRB00099445). All participants give informed consent before enrolling and participating. The study was also performed with approval from the FDA

A phase I study of the anaplastic lymphoma kinase inhibitor ceritinib in combination with gemcitabine-based chemotherapy in patients with advanced solid tumors

In this phase I, dose-escalation study, we sought to determine the maximum tolerated dose (MTD) of the anaplastic lymphoma kinase/c-ROS oncogene 1 receptor (ALK/ROS1) inhibitor ceritinib in combination with gemcitabine-based chemotherapy in patients with advanced solid tumors. Secondary objectives were characterization of the safety profile, pharmacokinetics and preliminary efficacy of these combinations, and identification of potential biomarkers of efficacy. Ceritinib was combined with gemcitabine (Arm 1), gemcitabine/nab-paclitaxel (Arm 2) or gemcitabine/cisplatin (Arm 3). Drug concentrations in plasma were measured by tandem mass spectrometric detection (LC-MS/MS). We analyzed archival tumor tissue for ALK, ROS1, hepatocyte growth factor receptor (c-MET) and c-Jun N-terminal kinase (JNK) expression by immunohistochemistry. Arm 2 closed early secondary to toxicity. Twenty-one patients were evaluable for dose-limiting toxicity (DLT). There was one DLT in Arm 1 (grade 3 ALT increase) and three DLTs in Arm 3 (grade 3 acute renal failure, grade 3 thrombocytopenia, grade 3 dyspnea). The MTD of ceritinib was determined to be 600 mg (Arm 1) and 450 mg orally daily (Arm 3). Main toxicities were hematologic, constitutional and gastrointestinal as expected by the chemotherapy backbone. The apparent clearance for ceritinib decreased substantially after repeated dosing; cisplatin did not significantly affect the pharmacokinetics of ceritinib. The overall response rate was 20%; the median progression-free survival was 4.8 months. Three out of five response-evaluable cholangiocarcinoma patients had clinical benefit. Increased expression of c-MET was associated with a lack of clinical benefit. Ceritinib in combination with gemcitabine and gemcitabine/cisplatin has a manageable toxicity profile. Further development of this strategy in tumors with ALK or ROS1 fusions is warranted.

Phase 1 study combining alisertib with nab-paclitaxel in patients with advanced solid malignancies

AIM

Aurora kinase A (AURKA) is a pleiotropic serine/threonine kinase that orchestrates mitotic progression. Paclitaxel stabilises microtubules and disrupts mitotic spindle assembly. The combination of AURKA inhibitor (alisertib) plus paclitaxel may be synergistic in rapidly proliferative cancers. We evaluated the safety and maximum tolerated dose (MTD) of alisertib in combination with nab-paclitaxel and its preliminary efficacy in patients with refractory high-grade neuroendocrine tumours (NETs).

METHOD

This is a two-part, Phase 1 study. In Part A (dose escalation), a standard 3 + 3 design was used to determine MTD. In Part B (dose expansion), patients with predominantly refractory high-grade NETs were enrolled.

RESULTS

In total, 31 patients were enrolled and treated (16 in Part A and 15 in Part B). The MTD of alisertib was 40 mg BID on D1-3 per week and nab-paclitaxel 100mg/m² weekly: 3 weeks, 1 week off. Dose-limiting toxicity was neutropenia, and other common side-effects included fatigue, mucositis, and diarrhoea. In Part A, a patient with small-cell lung cancer with partial response (PR) was treated for more than 2 years, whereas four other patients with pancreatic ductal adenocarcinoma (one patient), small cell lung cancer (SCLC) (two patients), or high-grade NET (one patient) achieved stable disease (SD). In Part B, 13 of 15 enrolled patients had high-grade NETs. Of these, one had PR, and four had SD for more than 10 months.

CONCLUSIONS

The combination of alisertib and nab-paclitaxel has manageable side-effect profile and showed promising preliminary efficacy in high-grade NETs, warranting further testing.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT01677559.

Cytotoxic T-lymphocyte infiltration and chemokine predict long-term patient survival independently of tumor mutational burden in triple-negative breast cancer

Background:

Cytotoxic T-lymphocyte (CTL) infiltration into tumor is a positive prognostic factor in breast cancer. High tumor mutational burden (TMB) is also considered as a predictor of tumor immunogenicity and response to immunotherapy. However, it is unclear whether the infiltration of functional CTL simply reflects the TMB or represents an independent prognostic value.

Methods:

Utilizing The Cancer Genome Atlas (TCGA) breast cancer cohort, we established the Functional Hotness Score (FHS). The associations of FHS and breast cancer patient prognosis as well as distinct immunity markers were analyzed in a total of 3011 breast cancer patients using TCGA, METABRIC and metastatic breast cancer (MBC) cohort GSE110590.

Results:

We established FHS, based on CD8A, GZMB and CXCL10 gene expression levels of bulk tumors, which delivered the best prognostic value among some gene combinations. Breast cancer patients with the high-FHS tumors showed significantly better survival. FHS was lower in the MBCs. Triple-negative breast cancer (TNBC) showed the highest FHS among subtypes. FHS predicted patient survival in hormone receptor (HR)-negative, especially in TNBC, but not in HR-positive breast cancer. FHS predicted patient prognosis independently in TNBC. The high-FHS TNBCs showed not only higher CD8+ T cell infiltration, but also enhanced broader type-1 anti-cancer immunity. The patients with the high-FHS tumors showed better prognosis not only in high-TMB tumors but also in low-TMB TNBCs. The combination of high-TMB with high-FHS identified a unique subset of patients who do not recur over time in TNBC.

Conclusion:

TNBCs with high FHS based on the expression levels of CD8A, GZMB and CXCL10 showed improved prognosis with enhanced anti-cancer immunity regardless of TMB. FHS constitutes an independent prognostic marker of survival, particularly robustly when combined with TMB in TNBC.

Abstract PS6-49: Intratumoral cytotoxic t-lymphocyte numbers and chemokine predict long-term survival of triple-negative breast cancer independently of tumor mutational burden

Background: Cytotoxic T-lymphocyte (CTL) infiltration into tumor is a positive prognostic factor in breast cancer. While high tumor mutation burden (TMB) is also considered as a predictor of tumor immunogenicity and response to immunotherapy. Triple-negative breast cancer (TNBC) has a higher TMB and accumulates more CTLs compared to other breast cancer subtypes. CTLs are identified by CD8 surface marker, which is encoded by CD8A gene. Granzyme B (GZMB) is a serine protease that is secreted by activated CTLs to induce apoptosis of the target cells. Chemokines, such as CXCL10 and CCL5 are key to the selective attraction of activated CTLs into tumors, as shown in multiple cancers. However, it remains unknown whether tumor infiltrating functional CTLs levels correlate with improved patient survival and are independent of TMB. In order to investigate it, we developed Functional Hotness Score (FHS) combining gene expressions of markers and attractants of activated CTL. Methods: Utilizing publicly available breast cancer cohorts, we established Functional Hotness Score (FHS), based on gene expression levels of CTL and chemokine markers in bulk tumors. The associations of FHS and breast cancer patient prognosis as well as distinct immunity markers were analyzed. Results: CD8, GZMB and CXCL10 combination resulted in the best prediction of the breas cancer patient prognosis. Thus, we established FHS based on the expression levels of these three genes. Breast cancer patients with the high-FHS tumors showed significantly better survival. FHS was lower in the metastatic breast cancers. Among breast cancer subtypes, triple-negative breast cancer (TNBC) showed the highest FHS. FHS predicted patient survival in hormone receptor (HR)-negative, especially TNBC, but not in HR-positive breast cancer. The high-FHS TNBCs showed not only higher CD8+ T cell infiltration, but also enhanced broader type-1 anti-cancer immunity. The patients with the high-FHS tumors showed better prognosis not only in high-TMB tumors but also in low-TMB TNBCs. The combination of high-TMB with high-FHS identified a unique subset of patients who do not recur over time. Conclusions: TNBCs with high-FHS based on the expression levels of CD8A, GZMB and CXCL10 showed improved prognosis with higher anti-cancer immunity regardless of TMB. FHS constitutes an independent prognostic marker of survival, particularly robust when combined with TMB in TNBCs.

Citation Format: Eriko Katsuta, Li Yan, Mateusz Opyrchal, Pawel Kalinski, Kazuaki Takabe. Intratumoral cytotoxic t-lymphocyte numbers and chemokine predict long-term survival of triple-negative breast cancer independently of tumor mutational burden [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS6-49.

Abstract PS2-09: Next generation sequencing (NGS) in older adults with breast cancer using tissue-based and circulating tumor DNA (ctDNA) assays

Background: With advances in next generation sequencing (NGS) and now approved targeted therapy in breast cancer, genomic testing to identify potentially actionable mutations has become a common practice in patients (pts) with advanced breast cancer using both ctDNA and traditional tissue-based assays. Less is known regarding physician practice patterns in obtaining NGS testing and the practical implications of testing in older adults with breast cancer.Methods: Pts with advanced breast cancer underwent molecular profiling using a plasma-based ctDNA NGS assay (Guardant360® or Tempus®) between 5/2015 and 5/2020 at Siteman Cancer Center. Pts with advanced breast cancer who underwent genomic profiling using a tissue-based NGS assay (Tempus®) between 12/2017 and 5/2020 at this institution were also included. Clinicopathological histories were obtained from the medical record. Correlations were examined using a Fisher’s exact test.Results: During 5/15-5/20, 244 pts underwent ctDNA testing and 147 pts had a tissue-based NGS assay performed. There was no significant difference between the number of pts ≥ 65 years-old who underwent ctDNA testing (n=78, 32.0%) and tissue testing (n=37, 25.2%). There was no statistically significant difference between date of metastatic diagnosis and date of NGS testing between the older and younger cohorts. In pts who underwent tissue-based NGS testing, there was no significant difference between site of tissue tested (distant recurrence vs local) in the older and younger cohorts. The most common clinical managements following both ctDNA and tissue-based testing are presented in Table 1. Out of the 391 pts who underwent testing, 27 pts had both ctDNA and tissue-based NGS performed. Pts ≥ 65 were less likely to have both assays performed (n=3, 11.1%; p&lt;0.05). In pts undergoing both assays, there were high concordance rates of ESR1 (81.5%) and PIK3CA (81.5%) mutations. Mean time between tissue and plasma collection for NGS testing in pts undergoing both assays was 356.4 days.

Conclusion: Older adults, who are typically less likely to be included in clinical trials, may still benefit from NGS to reveal potentially targetable mutations. It is reassuring in our cohort that older adults had ctDNA and tissue-based NGS performed at similar rates as part of standard of care treatment. The clinical management following NGS testing was also not significantly different in the older adult cohort. Older adults were less likely to have both tissue and ctDNA testing performed however, given the high concordance rates between tests, this may be less clinically relevant.

Table 1clinical management following NGS testing≥65 years-old&lt;65 years-oldp valueno actionable mutations41 (35.7%)123 (44.6%)p=0.1testing results saved for potential future use27 (23.5%)45 (16.3%)p=0.1change in management15 (13.0%)41 (14.9%)p=0.6

Citation Format: Katherine K Clifton, Jingqin Luo, Yu Tao, Jennifer Saam, Thereasa Rich, Timothy Rearden, Anna Roshal, Ashley Frith, Caron Rigden, Foluso Ademuyiwa, Katherine Weilbaecher, Leonel Hernandez Aya, Lindsay Peterson, Nusayba Bagegni, Rama Suresh, Ron Bose, Tanya Wildes, Mateusz Opyrchal, Cynthia Ma. Next generation sequencing (NGS) in older adults with breast cancer using tissue-based and circulating tumor DNA (ctDNA) assays [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS2-09.

Entinostat plus Pembrolizumab in Patients with Metastatic NSCLC Previously Treated with Anti-PD-(L)1 Therapy

PURPOSE

New therapies are needed to treat immune checkpoint inhibitor-resistant non-small cell lung cancer (NSCLC) and identify biomarkers to personalize treatment. Epigenetic therapies, including histone deacetylase inhibitors, may synergize with programmed cell death-1 (PD-1) blockade to overcome resistance. We report outcomes in patients with anti-programmed cell death ligand-1 [PD-(L)1]-resistant/refractory NSCLC treated with pembrolizumab plus entinostat in ENCORE 601.

PATIENTS AND METHODS

The expansion cohort of ENCORE 601 included patients with NSCLC who previously experienced disease progression with immune checkpoint inhibitors. The primary endpoint for the phase II expansion cohort is overall response rate (ORR); safety, tolerability, and exploratory endpoints are described.

RESULTS

Of 76 treated patients, 71 were evaluable for efficacy. immune-regulated RECIST-assessed ORR was 9.2% [95% confidence interval (CI): 3.8-18.1], which did not meet the prespecified threshold for positivity. Median duration of response was 10.1 months (95% CI: 3.9-not estimable), progression-free survival (PFS) at 6 months was 22%, median PFS was 2.8 months (95% CI: 1.5-4.1), and median overall survival was 11.7 months (95% CI: 7.6-13.4). Benefit was enriched among patients with high levels of circulating classical monocytes at baseline. Baseline tumor PD-L1 expression and IFNγ gene expression were not associated with benefit. Treatment-related grade ≥3 adverse events occurred in 41% of patients.

CONCLUSIONS

In anti-PD-(L)1-experienced patients with NSCLC, entinostat plus pembrolizumab did not achieve the primary response rate endpoint but provided a clinically meaningful benefit, with objective response in 9% of patients. No new toxicities, including immune-related adverse events, were seen for either drug. Future studies will continue to evaluate the association of monocyte levels and response.

Mutation profile differences in younger and older patients with advanced breast cancer using circulating tumor DNA (ctDNA)

PURPOSE

Little is known regarding the mutation profiles of ctDNA in the older adult breast cancer population. The objective of this study is to assess differences in mutation profiles in the older adult breast cancer population using a ctDNA assay as well as assess utilization of testing results.

METHODS

Patients with advanced breast cancer underwent molecular profiling using a plasma-based ctDNA NGS assay (Guardant360) between 5/2015 and 10/2019 at Siteman Cancer Center. The profiling results of a multi-institutional database of patients with advanced breast cancer who had undergone molecular profiling were obtained. Associations between mutations and age group (≥ 65 vs. < 65) were examined using a Fisher's exact test.

RESULTS

In the single-institutional cohort, 148 patients (69.2%) were < 65 years old and 66 patients (30.8%) ≥ 65 years old. ATM, BRAF, and PIK3CA mutations were found more frequently in older patients with ER + HER2- breast cancers (p < 0.01). In the multi-institutional cohort, 5367 (61.1%) were < 65 years old and 3417 (38.9%) ≥ 65 years old. ATM, PIK3CA, and TP53 mutations were more common in the older cohort (p < 0.0001) and MYC and GATA3 mutations were less common in the older cohort (p < 0.0001). CtDNA testing influenced next-line treatment management in 40 (19.8%) patients in the single-institutional cohort.

CONCLUSION

When controlling for subtype, results from a single institution were similar to the multi-institutional cohort showing that ATM and PIK3CA were more common in older adults. These data suggest there may be additional molecular differences in older adults with advanced breast cancers.

Abstract 6616: Functional hotness score generated by representative functional cytotoxic T-lymphocytes predicts long-term survival of triple-negative breast cancer independently to the tumor mutational burden

Background: Cytotoxic T-lymphocytes (CTLs) infiltration in a bulk tumor is a positive prognostic factor in breast cancer. CTL recognition is believed to react to mutation-induced neoantigens, thus, higher tumor mutation burden (TMB) is considered as an important predictor of tumor immunogenicity and response to immunotherapy. Although majority of breast cancer have low tumor mutation burden (TMB), triple-negative breast cancer (TNBC) has higher TMB compared to other breast cancer subtypes. However, it is unclear if the prognostic value high CTL infiltration depends on the TMB as the primary driver of enhanced anti-cancer immunity or represents an independent prognostic marker which can be used as a complement to TMB to predict patients' outcomes. CTLs are identified by CD8 marker, is encoded by CD8A. Granzyme B (GZMB) is a serine protease that is secreted by functionally-active CTLs to induce apoptosis of the target cells. CXCL10 is a chemokine which selectively attracts activated CTLs into subsets of other cancers; but its role in breast cancer remains unknown. We investigated if TNBC infiltrated with high levels of functional CTLs, so called “hot tumors”, have improved survival independently of their TMB.

Methods: Utilizing The Cancer Genome Atlas (TCGA) breast cancer cohort, we established Functional Hotness Score (FHS), based on the CD8A, GZMB and CXCL10 gene expression levels of bulk tumors. Total of 4149 breast cancer patients from publicly available multiple cohorts were analyzed to assess FHS and breast cancer patient prognosis as well as distinct immunity markers.

Results: FHS predicted the breast cancer patient survival better than each consisting gene. The breast cancer patients with high FHS tumors showed significantly better survival in the testing cohort (TCGA), which was further confirmed in the validation cohort (METABRIC). FHS was higher in the primary breast cancer tissues with metastasis compared to that without metastasis in TCGA. Further, FHS was higher in the metastatic tumors compared to the primary tumors in GSE110590. Among breast cancer subtypes, TNBC showed highest FHS compared to other subtypes in testing TCGA, which was validated in the METABRIC cohort. The patients with high FHS tumor demonstrated significantly better long-term survival than that with low FHS only in the hormone receptor (HR)-negative breast cancers, but not in the HR-positive tumors. The high FHS TNBCs showed higher not only CD8-positive T cell infiltration, but also a broader type-1 anti-cancer immunity. To investigate if FHS predicts patient survival independent of TMB, the patients were divided into high and low TMB groups. Interestingly, the higher FHS patients showed better prognosis not only in the high TMB group but also in the low TMB among TNBC patients. The combination of high TMB with high FHS identified the unique subset of the patients who did not recur over time.

Conclusion: In conclusion, TNBC with higher FHS based on the expression levels of CD8A, GZMB and CXCL10 showed improved prognosis with higher anti-cancer immunity regardless of TMB, and constituting an independent prognostic marker of survival, particularly when combined with TMB.

Citation Format: Eriko Katsuta, Li Yan, Mateusz Opyrchal, Pawel Kalinski, Kazuaki Takabe. Functional hotness score generated by representative functional cytotoxic T-lymphocytes predicts long-term survival of triple-negative breast cancer independently to the tumor mutational burden [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 6616.

Abstract 6426: Novel mechanism of PIM2 inhibition leads to significant effect on solid tumors

Background: PIM2 is overexpressed in hematopoietic and solid cancers, and is involved in multiple signaling pathways. In hematologic malignancies, PIM2 has been shown to be a pro-survival factor and demonstrated to be a possible therapeutic target. However, the role of PIM2 as a therapeutic target in solid cancers has not been fully elucidated.

Methods: PIM2 expression was compared between normal and cancer tissues in The Cancer Genome Atlas (TCGA) datasets. Pan-PIM inhibitor treatment, as well as PIM2 overexpression/knockdown technique was utilized to investigate the PIM2 role in solid cancers. Multiple cancer models were utilized for in vitro and in vivo experiments to investigate if PIM2 as a therapeutic target and examine mechanism of anti-tumor activity by JP11646.

Results: PIM2 was overexpressed in several types of cancer tissues, including breast, esophageal, head-neck, kidney, liver and endometrial cancers in TCGA. PIM2 overexpression promoted tumor growth in in vivo breast cancer mouse model. PIM2 inhibition by siRNA as well as pan-PIM inhibitor JP11646 activated apoptosis as seen by increased cleaved PARP. JP11646 treatment inhibited cancer cell proliferation in a dose-dependent manner in vitro in various types of solid cancers, including head-neck, ovarian, breast, prostate, liver, pancreatic, colorectal and non-small cell lung cancers. Interestingly, treatment with pan-PIM inhibitor JP11646 resulted in selective downregulation of PIM2 protein expression, but not PIM1 or PIM3 in breast cancer cell lines, BT549 and MDA-MB-231. The treatment also resulted in downregulation of phosphorylated downstream targets, 4EBP1 and TSC2 in breast cancer cells. However, additional proteasome inhibitor treatment blocked PIM2 downregulation and apoptosis activation was not seen. The result suggests that proteasome complex is required for PIM2 degradation which is necessary to induce apoptosis. JP11646 treatment inhibited tumor growth in breast, liver, pancreas, and non-small cell lung cancer in vivo xenograft models and was compared to multiple standard of care treatments showing advantage in lung tumors.

Conclusion: We found that PIM2 promoted cancer progression in solid tumors. We show novel mechanism of JP11646 targeting PIM2 for degradation and induction of apoptosis. We show that PIM2 may serve as a novel therapeutic target for multiple types of solid cancers with enhanced therapeutic effect through protein degradation rather than kinase inhibition alone.

Citation Format: Eriko Katsuta, Kazuaki Takabe, Alex Adjei, Mateusz Opyrchal. Novel mechanism of PIM2 inhibition leads to significant effect on solid tumors [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 6426.

Abstract CT139: Ceritinib (Cer) in combination with gemcitabine (Gem)-based chemotherapy in patients (pts) with advanced solid tumors, a phase I study

Introduction: Cer is an oral ALK/ROS1 inhibitor. Aberrancies in ALK and ROS1 have been observed in many cancer types and ALK inhibition has synergistic effects with chemotherapy in ALK or ROS1 rearranged tumors in preclinical models. We launched a Phase I study of Cer in combination with Gem-based chemotherapy in advanced solid tumors. Herein we present initial results of this study. Methods: Phase I, dose-escalation study of Cer in combination with A1: Gem 1000 mg IV D1/8/15 q28 days; A2: Gem 1000 mg IV + nanoparticle albumin-bound Paclitaxel 125 mg IV both D1/8/15 q28 days; A3: Gem 1000 mg IV + Cisplatin 60 mg IV D1/8 q21 days in pts with advanced, solid malignancies until disease progression, intolerable toxicity or withdrawal. A 3 + 3 dose-escalation design was used starting at Cer 450 mg once daily (DL1) in all arms; DL2 was 600 mg once daily. Primary objective was to determine the maximum tolerated dose (MTD) of Cer. Key inclusion criteria: diagnosis of advanced solid malignancy for which Gem-based treatment was appropriate, &gt;18 years old, ECOG PS 0/1, adequate bone marrow/renal/liver function. Key exclusion criteria: interstitial lung fibrosis/disease, recent acute coronary event, CHF NYHA III/IV, corrected QTc &gt; 450 ms. Pts in A3 could have up to 2 prior lines of therapy. Prior use of ALK inhibitors allowed. Plasma was collected for PK on C1D1, C2D1, and C1D15. Archival tumor tissue was tested for ALK/ROS1/JNK/MET by IHC. Results: Thirty-eight patients were enrolled with 21 evaluable for dose-limiting toxicity (DLT) in A1 and A3. A2 (n=4) closed to accrual for toxicity. Median age was 61 years. Seven pts (41%) had cholangiocarcinoma. A1 had one DLT (G3 ALT increase) in DL2; MTD was 600 mg. A3 had one DLT in DL1 (G3 acute renal failure) and two DLTs in DL2 (G3 thrombocytopenia and G3 dyspnea); MTD was 450 mg. G3-5 AEs in all pts: anemia (A1: 3/19, A3: 2/15), nausea (A1: 1/19, A3: 2/15), emesis (A1: 1/19, A3: 1/15), neutropenia (A1: 2/19, A3: 8/15), thrombocytopenia (A1: 1/19, A3: 4/15), hyperbilirubinemia (A3: 3/15), pneumonia (A1: 2/19), acute renal failure (A3: 1/15), fatigue (A3: 2/15). Fifteen patients were evaluable for response; the overall response rate was 20% with two PR (pt with head and neck carcinoma in A1 and pt with carcinoma of unknown primary in A3) - and one CR in a pt with cholangiocarcinoma (A3) lasting 10.3 months. Overall, disease control rate was 47%. Of 5 evaluable pts with cholangiocarcinoma 3 had clinical benefit. Median PFS 3.4 mo (A1)/4.8 mo (A3) and OS 13.7 mo (A1)/29.1 mo (A3). PK and IHC data will be presented at the conference. Conclusions: The MTD of Cer is 600 mg in combination with Gem and 450 mg in combination with Gem/Cisplatin. Further evaluation of Cer plus Gem-based chemotherapy is planned in ALK/ROS1 positive cholangiocarcinomas.

Citation Format: Christos Fountzilas, Alex Adjei, Mateusz Opyrchal, Rachel Evans, Kristopher Attwood, Andrew Goey, John Wilton, Wen Wee Ma, Renuka Iyer. Ceritinib (Cer) in combination with gemcitabine (Gem)-based chemotherapy in patients (pts) with advanced solid tumors, a phase I study [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 CT139.

Outcome of Everolimus-Based Therapy in Hormone-Receptor-Positive Metastatic Breast Cancer Patients After Progression on Palbociclib

Background

Despite the approval of mTOR inhibitor everolimus and CDK4/6 inhibitors in the management of hormone-receptor-positive HER2 non-amplified metastatic breast cancer (HR+ HER2-MBC), the optimal sequence of therapy is unclear. There are no clinical data on efficacy of everolimus in HR+ HER2-MBC after cancer progresses on CDK4/6 inhibitors.

Objective

The objective of this study is to find the efficacy of everolimus in HR+ HER2-MBC after they progress on a CDK4/6 inhibitor palbociclib.

Methods

This is a retrospective, 2-institute review of HR+ HER2-MBC from Jan 2015 to March 2018 treated with everolimus after progression on palbociclib. Primary end point was median progression-free survival (PFS), secondary end points objective response rate (ORR), clinical benefit ratio (CBR), and overall survival (OS).

Results

Out of 41 women with median age 61 years (33, 87) enrolled, 66% had received adjuvant systemic therapy, 61% had visceral disease, and 95% had prior nonsteroidal aromatase inhibitors. About 83% women had 3 or more chemotherapy or hormonal therapies prior to everolimus. Kaplan-Meier estimates showed a median PFS of 4.2 months (95% confidence interval [CI]: 3.2-6.2). The median OS was 18.7 months (95% CI 9.5 to not reached). Objective response rate and CBR were both 17.1%.

Conclusion

Everolimus was associated with modest PFS and ORR in HR+ HER2-MBCs postprogression on palbociclib.

Contribution of Immune Cells to Glucocorticoid Receptor Expression in Breast Cancer

Breast cancer (BC) patients experience increased stress with elevated cortisol levels, increasing risk of cancer recurrence. Cortisol binds to a cytoplasmic receptor, glucocorticoid receptor (GR) encoded by GR gene (NR3C1). We hypothesized that not only cancer cells, but even immune cells in the tumor microenvironment (TME) may contribute to GR expression in bulk tumor and influence prognosis. To test this, mRNA expression data was accessed from METABRIC and TCGA. "High" and "low" expression was based on highest and lowest quartiles of NR3C1 gene expression, respectively. Single-cell sequencing data were obtained from GSE75688 and GSE114725 cohorts. Computer algorithms CIBERSORT, Gene Set Enrichment Analysis and TIMER were used. GR-high BC has better median disease-free and disease-specific survival. Single cell sequencing data showed higher GR expression on immune cells compared to cancer and stromal cells. Positive correlation between GR-high BC and CD8⁺ T-cells was noted. In GR-high tumors, higher cytolytic activity (CYT) with decreased T-regulatory and T-follicular helper cells was observed. High GR expression was associated with lower proliferation index Ki67, enriched in IL-2_STAT5, apoptosis, KRAS, TGF-β signaling, and epithelial-to-mesenchymal transition. Immune cells significantly contribute to GR expression of bulk BC. GR-high BC has a favorable TME with higher CYT with favorable outcomes.

Mutation profile differences in younger and older patients with advanced breast cancer using circulating tumor DNA (ctDNA)

1089

Background: Although the noninvasive nature of ctDNA testing is attractive in an older adult population, less is known regarding the mutation profiles of ctDNA in the older adult breast cancer population as this population is often excluded from studies. Previous tissue testing has shown differences in mutation profiles between older and younger adults with breast cancer. The objective of this study is to assess differences in mutation profiles in the older and younger adult breast cancer population using a ctDNA assay. Methods: Patients (pts) with advanced breast cancer underwent molecular profiling using a plasma-based ctDNA NGS assay (Guardant360) between 5/2015-10/2019 at Siteman Cancer Center. Clinicopathological histories were obtained from the medical record. The results of a multicenter database of pts with advanced breast cancer who had undergone molecular profiling using Guardant360 were obtained. Associations between mutations and age were measured using a Fisher’s exact test. Results: In the single institution cohort, of the 214 patients who underwent testing, 148 (69.16%) were < 65 and 66 (30.84%) ≥ 65 years-old. The most frequently mutated genes in age < 65 pts were TP53 (48.65%), PIK3CA (35.81%), and ESR1 (30.41%) while the most frequently mutated genes in age≥65 pts were PIK3CA (56.06%), TP53 (51.52%), ESR1 (25.76%), and ATM (21.21%). ATM, BRAF and PIK3CA mutations were found more frequently in age≥ 65 pts with ER+ HER2- breast tumors (p < 0.01). MYC and ESR1 mutations were not significantly associated with age, overall or within subtype. Overall ctDNA resulted in change in management in 19.8% pts (40/202). In the larger multicenter cohort, of the 8803 pts who underwent testing, 5367 (61.0%) were < 65 and 3417 (38.8%) ≥ 65 years-old. ATM, ESR1 and PIK3CA mutations were more common in age≥65 pts (p < 0.0001) and MYC mutations were less common in age≥65 pts (p < 0.0001). Conclusions: This study found that ctDNA is a feasible, attractive alternative to traditional biopsies and may identify actionable mutations in older adults with breast cancer. When controlling for subtype, results from a single institution were similar to the larger multicenter cohort showing ATM and PIK3CA were more common in the older adult population. This data suggests there may be additional molecular differences between breast cancer in older compared to younger adults that warrants further investigation.

Functional hotness score based on three genes predicts long-term survival of triple-negative breast cancer independent from tumor mutational burden

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Background: Cytotoxic T-lymphocytes (CTLs) infiltration into tumor is a positive prognostic factor in breast cancer. Infiltration of CTLs are believed to be driven by mutation-induced neoantigens, thus, higher tumor mutation burden (TMB) is considered an important predictor of tumor immunogenicity and response to immunotherapy, but the association between intratumoral CTL counts and TMB in the overall cancer prognosis remains unclear. Methods: Utilizing publicly available breast cancer cohorts, we established Functional Hotness Score (FHS), based on CD8A, GZMB and CXCL10 gene expression levels of bulk tumors. The associations of FHS and breast cancer patient prognosis as well as distinct immunity markers were analyzed. Results: Breast cancer patients with high-FHS tumors demonstrated significantly better survival. FHS was lower in metastatic breast cancer. Among breast cancer subtypes, triple-negative breast cancer (TNBC) showed the highest FHS. FHS predicted patient survival not in hormone receptor (HR)-positive but in HR-negative, especially TNBCs. The high-FHS TNBCs enhanced not only CD8+ T cell infiltration, but also a broader type-1 anti-cancer immunity. The patients with the high-FHS patients showed better prognosis not only in high-TMB tumors but also in low-TMB TNBCs. The combination of high-TMB with high-FHS identified the unique subset of patients who did not recur over time. Conclusions: In conclusion, TNBCs with high-FHS based on the expression levels of CD8A, GZMB and CXCL10 showed improved prognosis with higher anti-cancer immunity regardless of TMB, and constituting an independent prognostic marker of survival, particularly robust when combined with TMB.

Abstract P4-05-16: Immune landscape of glucocorticoid receptor high breast cancer

BACKGROUND: Glucocorticoid receptor (GR) activation is pro-apoptotic in lymphoid malignancies, whereas in estrogen-receptor negative (ER-) breast cancer, GR activation is anti-apoptotic and associated with relapse through a direct transcriptional role in tumor cells. A meta-analysis of GEO dataset has shown that higher GR expression is associated with an improved relapse free survival (RFS) in ER+ breast cancer but a worse RFS in triple negative breast cancer (TNBC). The relative contributions of GR expression on tumor vs. immune cells which may influence outcomes have not been studied. We hypothesize that there is a difference in the immune landscape between GR-high and GR-low tumors. METHODS: mRNA expression data was accessed from The Cancer Genome Atlas (TCGA) and METABRIC. K-clustering classified GR gene (NR3C1) expression into “high” and “low”. Computer algorithms TIMER, CIBERSORT, Immune pathway gene score, and cytolytic activity score (CYT) were used. Single-cell sequencing data were obtained from GSE75688 and GSE114725 cohorts. RESULTS: 1904 and 1087 pts with stage I-III breast cancer had clinical and genomic data available in METABRIC and TCGA respectively. GR-high tumors had better median overall survival (mOS) [15 vs. 12yrs {HR 0.8(0.71-0.9), p&lt;0.001}] in METABRIC, however, no significant difference observed in TCGA. GR-high tumors also had better median disease-specific survival (mDSS) [25 vs. 23.5yrs {HR 0.79 (0.67-0.93), p=0.005}] in METABRIC and [NR vs. NR {HR 0.4 (0.23-0.81), p=0.004}] in TCGA. Hormone receptor (HR) + subtype had better mOS [15.2 vs. 12.8yrs {HR 0.98(0.75-1), p=0.021}] but no significant difference in mDSS in GR-high vs. -low tumors in METABRIC; however, TCGA showed better mDSS [NR vs. NR {HR 0.4(0.22-0.92), p=0.049}]. TNBC subtype was associated with better mOS [17 vs. 7.4yrs {HR 0.66(0.48-0.9)}, p=0.0094] and mDSS [NR vs. 20yrs {HR 0.67(0.46-0.98)}, p=0.038] in GR-high vs. -low tumors in METABRIC; however, no significant differences were observed in TCGA. GR-high tumors had significantly higher number of immunomodulatory cells [B-cells, dendritic cells and mast cells] (p&lt;0.001) and lower number of immunosuppressive cells [T regulatory cells (Treg) and T follicular helper cells] (p&lt;0.001). There was a moderate correlation between GR-high and high CD8+T-cells (r=0.49, p=0.001) and macrophages (r=0.35, p=0.02). GR-high tumors had increased macrophages, lymphocyte infiltration and TGF-β response (p&lt;0.001). Significantly higher expression of T-cell exhaustion genes PD-1, PD-L1, CTLA-4, IDO1 and TIM3 was observed in GR-high tumors (p&lt;0.001). Strikingly, single cell sequencing data showed higher GR expression on immune cells (T-cells, B-cells and myeloid cells) compared to stromal or tumor cells (p&lt;0.001), with significantly higher GR expression on CD8+T-cells compared to other immune cell subsets including Treg, CD4+T-cells, neutrophils, monocytes, dendritic cells, mast cells and macrophages (p&lt;0.001). These findings explain why CYT was consistently elevated in GR-high tumors (p=0.001) observed both in TCGA and METABRIC. CONCLUSIONS: This study demonstrates that there are significant differences in the immune cell landscape in GR-high vs. GR-low tumors, suggesting that a higher immune cell infiltration accounts for greater anti-tumor cytolytic activity in GR high tumors. Thus, in addition to a direct transcriptional role for GR on tumor cells, contribution to outcomes by immune cells should also be acknowledged. Further studies examining the important contribution of factors causing activation/inactivation of immune cells in tumor microenvironment and their effects on clinical outcomes are warranted.

Citation Format: Shipra Gandhi, Ahmed Elkhanany, Mateusz Opyrchal, Elizabeth A Repasky, Kazuaki Takabe. Immune landscape of glucocorticoid receptor high breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-05-16.

Abstract P3-07-07: Functional hotness score of cytotoxic T-lymphocytes infiltration to predicts outcome of triple-negative breast cancer patients

Introduction: Cytotoxic T-lymphocytes (CTLs) infiltration into tumor has been shown to predict better prognosis in breast cancer. Triple-negative breast cancer (TNBC) has been shown to have higher immunogenicity and enhanced CTL attraction. CD8A is a surface marker of CTLs and Granzyme B (GZMB) is a serine protease, secreted by CTLs to mediate apoptosis of the target cells. CXCL10 is a chemokine, which is known to attract CTLs into tumors in some types of cancers. However, the impact of CXLC10 expression and its role in the CTL attraction to TNBC remain unknown. Therefore, we hypothesized that Functional Hotness Score (FHS) that incorporate expressions of CXLC10 and CTL markers associates with anti-cancer immune cell infiltration and better survival of TNBC independent of mutation burden. Methods: Based on CD8A, GZMB and CXCL10 expression levels of the tumor, we established Functional Hotness Score (FHS) utilizing The Cancer Genome Atlas (TCGA) breast cancer cohort. As a validation cohort, METABRIC cohort was utilized. As neoadjuvant chemotherapy cohort, GSE20271, GSE20194, GSE22093, GSE23988, GSE25066 and GSE28844 from Gene Expression Omnibus (GEO) were utilized. As metastatic breast cancer dataset, GSE110590 from GEO was utilized. Gene Set Enrichment Analysis (GSEA) was conducted utilizing hallmark gene sets. Infiltrated immune cell fraction was estimated by CIBERSROT algorithm. Results: Out of 6 neoadjuvant cohorts, 5 cohorts showed higher CXCL10 expression levels in pathological completely response (pCR) tumors compared to residual tumors (RD). On the other hand, 1 and 3 cohorts showed higher expression levels of CD8A and GZMB in pCR tumors, respectively. Utilizing these 3 gene expression levels and hazard ratio of overall survival (OS) of the patients, prognostic Functional Hotness Score (FHS) was developed. As we expected, patients with High FHS tumors showed significantly better OS in TCGA cohort (p=0.006). This finding was validated in METABRIC cohort. In the metastatic breast cancer cohort, metastatic tumors showed lower FHS compared to primary tumors, such as liver (p=0.003) and lung metastases (p=0.031). Whereas, most of the brain metastases tissues showed similar level of FHS compared to primary tumors (p=0.068). Subgroup analysis based on subtype revealed that TNBC showed highest FHS among each subtype with wide variation. TNBC was the only subtype that high FHS showed better OS (p=0.001). High FHS TNBC significantly enriched immune response related gene sets, such as allograft rejection (p&lt;0.001), complement (p&lt;0.001), IFN-γ response (p&lt;0.001), IL2/STAT5 signaling (p&lt;0.001), inflammatory response (p=0.002), IL6/JAK/STAT3 signaling (p&lt;0.001) and IFN-α response (p&lt;0.001). High FHS TNBC showed higher anti-cancer immune cell infiltration, such as CD8+ T lymphocytes, activated memory CD4+ T lymphocytes, γδ T lymphocytes, memory B lymphocytes and M1 macrophage, and lower resting or pro-cancer immune cells such as resting CD4+ T lymphocytes, regulatory T lymphocytes, naïve B lymphocytes and M2 macrophages. There was no correlation between FSH and mutation count (r=0.443). To investigate if the prognostications of FHS are associated with mutation burden, we stratified TNBC into high and low mutation burden group. Interestingly, higher FHS showed better OS regardless mutation burden (high mutation; p=0.019, low mutation; p=0.049) in TNBC. Conclusion: In conclusion, TNBC with higher FHS based on the expression levels of CD8A, GZMB and CXCL10 showed improved prognosis with higher immune cell infiltration and immune reaction regardless mutation burden.

Citation Format: Eriko Katsuta, Li Yan, Mateusz Opyrchal, Pawel Kalinski, Kazuaki Takabe. Functional hotness score of cytotoxic T-lymphocytes infiltration to predicts outcome of triple-negative breast cancer patients [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-07-07.

Abstract P1-19-03: JAVELIN PARP Medley, a phase 1b/2 study of avelumab plus talazoparib: Results from advanced breast cancer cohorts

Background: Avelumab, a human IgG1 anti–PD-L1 monoclonal antibody, has shown antitumor activity and a manageable safety profile in several tumor types. Talazoparib, an orally available PARP inhibitor, is approved for the treatment of patients with deleterious or suspected deleterious germline BRCA1/2-mutated HER2− locally advanced (LA) or metastatic (M) breast cancer (BC). Preclinical data suggest that PARP inhibitors may have synergistic activity when administered in combination with immune checkpoint inhibitors. We report results from patients with LA/MBC enrolled in the phase 1b/2, multicohort JAVELIN PARP Medley study (NCT03330405).

Methods: In phase 1b (cohort 1), patients with advanced solid tumors who had received ≥1 prior standard of care chemotherapy (CT) regimen were treated with avelumab 800 mg IV every 2 weeks (Q2W) in combination with talazoparib 1.0 mg orally once daily (QD) (dose de-escalation to 0.75 or 0.5 mg permitted following toxicity). In 2 phase 2 cohorts, eligible patients had either LA/M triple-negative BC (TNBC, cohort 2A) or LA/M hormone receptor positive (HR+), HER2−, DNA damage repair defect-positive BC (cohort 2B). Patients in cohort 2A had received 0 to 2 prior CT regimens (no progression on prior platinum-based CT) and patients in cohort 2B had received prior standard of care hormone therapy in either the adjuvant and/or LA/M setting followed by 0 to 2 prior CT regimens (no progression on prior platinum-based CT). The primary endpoint for phase 1b was first-cycle dose-limiting toxicities (DLTs) and for phase 2 was objective response (investigator assessed per RECIST v1.1). Adverse events (AEs) were characterized using National Cancer Institute Common Terminology Criteria for AEs v4.03.

Results: By the data cutoff on December 24, 2018, 34 patients had been treated in cohorts 1 and 2. Twelve patients with advanced solid tumors were treated in cohort 1 (including 2 patients with TNBC); 3 patients (25.0%) had a first-cycle DLT: grade 3 neutropenia, (n=1) and grade 3 thrombocytopenia, (n=2). Best overall response (BOR) was partial response (PR) in 1 patient, stable disease (SD) in 3, progressive disease (PD) in 6, and non-complete response/non-PD in 1 patient with metastatic castration-resistant prostate cancer and non-measurable disease at baseline; 1 patient was not evaluable for response. Both patients with TNBC had a BOR of SD and remained on treatment for ≥9 months. Objective response rate in this pre-treated and heterogenous population was 8.3% (95% CI, 0.2, 38.5). Based on the phase 1b data, the recommended phase 2 dose was avelumab 800 mg Q2W and talazoparib 1 mg QD. By data cutoff, 22 patients had been treated in cohorts 2A (n=19) and 2B (n=3); median age was 56 and 50 years, respectively. In cohort 2A, 12 patients were evaluable for disease assessment; BOR was PR in 1, SD in 6, and PD in 5. All 3 patients in cohort 2B were non-evaluable for response at data cutoff. Treatment-related AEs (TRAEs) of any grade occurred in 11 patients (91.7%) in cohort 1, and 18 (94.7%) patients in cohort 2A. In cohort 2A, the most common TRAEs were anemia (57.9%), nausea (26.3%), fatigue (21.1%) and thrombocytopenia (21.1%); 9 patients (47.4%) had grade ≥3 TRAEs. There were no treatment-related deaths. Safety data from cohort 2B are not reported owing to low patient numbers. Observed pharmacokinetic (PK) data for avelumab 800 mg Q2W were similar to simulated data derived from a population PK model developed using 10 mg/kg dosing.

Conclusions: Avelumab 800 mg Q2W administered in combination with talazoparib 1 mg QD in patients with advanced solid tumors, showed preliminary antitumor activity and a manageable safety profile, which was comparable to the safety profiles of the single agents. The study is ongoing; updated safety and efficacy data, and biomarker data will be presented.

Citation Format: Timothy A Yap, Panagiotis Konstantinopoulos, Melinda L. Telli, Smita Saraykar, J Thaddeus Beck, Matthew D. Galsky, Jame Abraham, David R. Wise, Mustafa Khasraw, Gabor Rubovszky, Mikhail Dvorkin, Anil A Joy, Mateusz Opyrchal, Daria Stypinski, Colombe Chappey, Ross Stewart, Rossano Cesari, Anita Scheuber, Aditya Bardia. JAVELIN PARP Medley, a phase 1b/2 study of avelumab plus talazoparib: Results from advanced breast cancer cohorts [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-19-03.

Abstract P6-07-04: Mechanosensing calcium channel PIEZO2 accelerates epithelial-mesenchymal transition in triple-negative breast cancer

Introduction: Breast cancer is the most common female malignancy. Despite improvements in therapeutic options, metastatic disease remains incurable with limited treatments especially in triple-negative breast cancer (TNBC). Clinical outcomes in patients with TNBC continue to be worse as compared to other breast cancer subtypes. Therefore, novel therapeutic targets for TNBC are in urgent need. PIEZO2, which is a transmembrane calcium channel, is known to function as a channel-type mechanosensor in various aspects of mechanotransduction. Recently there have been reports that PIEZO2 may be involved in carcinogenesis and cancer progression. However, the role of PIEZO2 in breast cancer has not been elucidated. We hypothesized that PIEZO2 plays significant roles in progression of TNBC. Methods: To investigate the role of PIEZO2 in human breast cancer patients, The Cancer Genome Atlas (TCGA) breast cancer cohort, in which there are mRNA expression data from RNA-seq and clinical data, was utilized. PIEZO2 expression level was compared among breast cancer subtypes. Patients’ survival was compared based on PIEZO2 expression in each subtype. We used gene set enrichment analysis (GSEA) algorithm to evaluate pathways associated with PIEZO2 expression. To further elucidate the mechanisms of PIEZO2 roles, TNBC cell line, MDA-MB-231 was utilized for in vitro experiments. PIEZO2 expression was downregulated by small interfering RNA (siRNA). Cell viability was quantified by MTT assay. Protein expression was compared by western blot. Results: Breast cancer showed the highest PIEZO2 expression level, among various types of cancers in TCGA. In the breast cancer cohort, PIEZO2 expression level was lower in the TNBC subtype compared to other subtypes (p&lt;0.001). Thus we hypothesized that PIEZO2 has different roles in each subtype. Survival analyses revealed that patients with high expression of PIEZO2 tumors showed significantly worse overall survival (p=0.016) in the TNBC cohort. However, there was no significant difference in the hormone receptor (HR)-positive (p=0.555) and the HER2-positive (p=0.380) cohorts. To explore underlying mechanisms how PIEZO2 high expressing tumors associate with worse prognosis in TNBC, GSEA was conducted. PIEZO2 high expressing tumors enriched epithelial-mesenchymal transition (EMT; NES=1.90, p=0.012) and Angiogenesis (NES=1.91, p&lt;0.001) gene sets, as well as TAZ/YAP gene set (NES=1.57, p=0.028). PIEZO2 knockdown by siRNA significantly suppressed cell viability. This finding was validated by PIEZO inhibitor GSMTx-4 treatment. Further, expression levels of EMT related proteins, such as Vimentin and Snail, were downregulated in the PIEZO2 knockdown MDA-MB-231 cells compared to control cells. Conclusion: We describe a novel signaling pathway mediated by PIEZO2 leading to worse clinical outcomes in patients with TNBC by activation of EMT. Further work is ongoing to validate PIEZO2 as a novel therapeutic target for TNBC.

Citation Format: Eriko Katsuta, Marija Vujcic, Shipra Gandhi, Arthur Beyder, Kazuaki Takabe, Mateusz Opyrchal. Mechanosensing calcium channel PIEZO2 accelerates epithelial-mesenchymal transition in triple-negative breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P6-07-04.

Chimeric Antigen Receptor-T Cells for Targeting Solid Tumors: Current Challenges and Existing Strategies

Chimeric antigen receptor-T cells (CAR-Ts) are an exciting new cancer treatment modality exemplified by the recent regulatory approval of two CD19-targeted CAR-T therapies for certain B cell malignancies. However, this success in the hematological setting has yet to translate to a significant level of objective clinical responses in the solid tumor setting. The reason for this lack of translation undoubtedly lies in the substantial challenges raised by solid tumors to all therapies, including CAR-T, that differ from B cell malignancies. For instance, intravenously infused CAR-Ts are likely to make rapid contact with cancerous B cells since both tend to reside in the same vascular compartments within the body. By contrast, solid cancers tend to form discrete tumor masses with an immune-suppressive tumor microenvironment composed of tumor cells and non-tumor stromal cells served by abnormal vasculature that restricts lymphocyte infiltration and suppresses immune function, expansion, and persistence. Moreover, the paucity of uniquely and homogeneously expressed tumor antigens and inherent plasticity of cancer cells provide major challenges to the specificity, potency, and overall effectiveness of CAR-T therapies. This review focuses on the major preclinical and clinical strategies currently being pursued to tackle these challenges in order to drive the success of CAR-T therapy against solid tumors.

Recruitment of Intratumoral CD103+ Dendritic Cells by a CXCR4 Antagonist-Armed Virotherapy Enhances Antitumor Immunity

Intratumoral dendritic cells play an important role in stimulating cytotoxic T cells and driving antitumor immunity. Using a metastatic ovarian tumor model in syngeneic mice, we explored whether therapy with a CXCR4 antagonist-armed oncolytic vaccinia virus activates endogenous CD103+ dendritic cell responses associated with the induction of adaptive immunity against viral and tumor antigens. The overall goal of this study was to determine whether expansion of CD103+ dendritic cells by the virally delivered CXCR4 antagonist augments overall survival and in situ boosting with a tumor antigen peptide-based vaccine. We found that locoregional delivery of the CXCR4-A-armed virus reduced the tumor load and the immunosuppressive network in the tumor microenvironment, leading to infiltration of CD103+ dendritic cells that were capable of phagocytic clearance of cellular material from virally infected cancer cells. Further expansion of tumor-resident CD103+ DCs by injecting the FMS-related tyrosine kinase 3 ligand, the formative cytokine for CD103+ DCs, provided a platform for a booster immunization with the Wilms tumor antigen 1 peptide-based vaccine delivered intraperitoneally with polyriboinosinic:polyribocytidylic acid as an adjuvant. The vaccine-induced antitumor responses inhibited tumor growth and increased overall survival, indicating that expansion of intratumoral CD103+ dendritic cells by CXCR4-A-armed oncovirotherapy treatment can potentiate in situ cancer vaccine boosting.

Oncologist uptake of comprehensive genomic profile guided targeted therapy

We describe the extent to which comprehensive genomic profiling (CGP) results were used by oncologists to guide targeted therapy selection in a cohort of solid tumor patients tested as part of standard care at Roswell Park Comprehensive Cancer Center June 2016-June 2017, with adequate follow up through September 2018 (n = 620). Overall, 28.4% of CGP tests advised physicians about targeted therapy use supported by companion diagnostic or practice guideline evidence. Post-test targeted therapy uptake was highest for patients in active treatment at the time of order (86% versus 76% of treatment naïve patients), but also took longer to initiate (median 50 days versus 7 days for treatment naïve patients), with few patients (2.6%) receiving targeted agents prior to testing. 100% of patients with resistance variants did not receive targeted agents. Treatment naïve patients received immunotherapy as the most common alternative. When targeted therapy given off-label or in a trial was the best CGP option, (7%) of patients received it. Our data illustrate the appropriate and heterogeneous use of CGP by oncologists as a longitudinal treatment decision tool based on patient history and treatment needs, and that some patients may benefit from testing prior to initiation of other standard treatments.

Abstract CT072: Efficacy and safety of entinostat (ENT) and pembrolizumab (PEMBRO) in patients with melanoma previously treated with anti-PD1 therapy

Background: Inhibitors of programmed death 1 (PD-1) and its ligand (PD-L1) have improved outcomes in patients (pts) with advanced melanoma, but treatment options for pts who progress on or after these therapies remain limited. In this group, we previously reported preliminary data that ENT, a class I selective histone deacetylase (HDAC) inhibitor, in combination with PEMBRO showed promising activity, through alteration of the immunosuppressive tumor microenvironment. Here we report the full cohort of patients enrolled.

Methods: ENCORE-601 is an open-label study evaluating ENT (5 mg PO weekly) + PEMBRO (200 mg IV Q3W) in pts with unresectable or metastatic melanoma who were previously treated with a PD-1-blocking antibody and experienced progression on or after therapy. A Simon 2-stage design was utilized (Stage 1: 13 patients, Stage 2: 40 patients) and the primary endpoint was ORR as assessed by irRECIST. Tumor biopsies and blood samples for immune correlates were obtained pre- and on-treatment.

Results: 53 patients were enrolled (the last patient entered April 2018, data cutoff is January 2018). The median duration of prior PD-1 therapy was 4.9 months and median time from last dose to study entry was 2.7 months (66% of patients had no intervening therapy between their prior PD-1 therapy and study enrollment). Additional baseline demographics are as follows: 55% were ECOG 0, 36% had elevated LDH, 70% pts had prior ipilimumab, and 23% had prior BRAF/MEK inhibitors. The confirmed objective response with ENT + PEMBRO is 19% (1 CR and 9 PRs; 95% CI: 9-32%); these results exceed the threshold for success based on the prespecified design. The median duration of response as of the cut-off date is 12.5 months (range 4-18 months) with 5 responders ongoing at the time of data cutoff. An additional 7 patients have had stable disease for &gt; 6 months, resulting in a clinical benefit rate (CR, PR, SD &gt; 6 months) of 32% (95% CI: 20%-46%). The median PFS is 4.2 months. Efficacy results in patients who received prior ipilimumab were consistent with the overall population. Among the responders, best response on prior PD-1 therapy were as follows: progression- 3 pts, stable disease- 5 pts, partial response- 1 pt, unknown- 1 pt. Grade 3/4 related AEs occurring in &gt;5% of patients included neutropenia, fatigue, and hyponatraemia. 5 patients (9%) experienced a Grade 3/4 immune-related AE (2 events of rash, 1 each of colitis, pneumonitis, and autoimmune hepatitis). Additional correlative analyses to identify biomarkers of response, including whole exome sequencing and RNAseq, are in progress.

Conclusions: In patients with melanoma who have progressed following treatment with prior PD-1 blockade, and both prior PD-1 and CTLA-4 blockade, ENT plus PEMBRO demonstrates significant clinical activity and acceptable safety.

Citation Format: Ryan J. Sullivan, Stergios J. Moschos, Melissa L. Johnson, Mateusz Opyrchal, Peter Ordentlich, Susan Brouwer, Serap Sankoh, Michael L. Meyers, Sanjiv S. Agarwala. Efficacy and safety of entinostat (ENT) and pembrolizumab (PEMBRO) in patients with melanoma previously treated with anti-PD1 therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT072.