Bintrafusp Alfa, a Bifunctional Fusion Protein Targeting TGF-β and PD-L1, in Patients With Non-Small Cell Lung Cancer Resistant or Refractory to Immune Checkpoint Inhibitors

BACKGROUND

Bintrafusp alfa is a first-in-class bifunctional fusion protein composed of the extracellular domain of transforming growth factor beta receptor II (a TGF-β "trap") fused to a human immunoglobulin G1 monoclonal antibody blocking programmed cell death 1 ligand 1 (PD-L1). We report the efficacy and safety in patients with non-small cell lung cancer (NSCLC) that progressed following anti-PD-(L)1 therapy.

MATERIALS AND METHODS

In this expansion cohort of NCT02517398-a global, open-label, phase I trial-adults with advanced NSCLC that progressed following chemotherapy and was primary refractory or had acquired resistance to anti-PD-(L)1 treatment received intravenous bintrafusp alfa 1200 mg every 2 weeks until confirmed progression, unacceptable toxicity, or trial withdrawal. The primary endpoint was best overall response (by Response Evaluation Criteria in Solid Tumors version 1.1 adjudicated by independent review committee); secondary endpoints included safety.

RESULTS

Eighty-three eligible patients (62 [74.7%] treated with ≥3 prior therapies) received bintrafusp alfa. Four patients (3 primary refractory, 1 acquired resistant) had confirmed partial responses (objective response rate, 4.8%; 95% CI, 1.3%-11.9%), and 9 had stable disease. Tumor cell PD-L1 expression was not associated with response. Nineteen patients (22.9%) experienced grade ≥3 treatment-related adverse events, most commonly asthenia (3 [3.6%]) and fatigue, eczema, and pruritus (2 each [2.4%]). One patient had grade 4 amylase increased. One patient died during treatment for pneumonia before initiation of bintrafusp alfa.

CONCLUSION

Although the primary endpoint was not met, bintrafusp alfa showed some clinical activity and a manageable safety profile in patients with heavily pretreated NSCLC, including prior anti-PD-(L)1 therapy. Tumor responses occurred irrespective of whether disease was primary refractory or had acquired resistance to prior anti-PD-(L)1 therapy.

Identification of HMGA2 as a predictive biomarker of response to bintrafusp alfa in a phase 1 trial in patients with advanced triple-negative breast cancer

Background

We report the clinical activity, safety, and identification of a predictive biomarker for bintrafusp alfa, a first-in-class bifunctional fusion protein composed of the extracellular domain of TGFβRII (a TGF-β "trap") fused to a human IgG1 mAb blocking PD-L1, in patients with advanced triple-negative breast cancer (TNBC).

Methods

In this expansion cohort of a global phase 1 study, patients with pretreated, advanced TNBC received bintrafusp alfa 1200 mg every 2 weeks intravenously until disease progression, unacceptable toxicity, or withdrawal. The primary objective was confirmed best overall response by RECIST 1.1 assessed per independent review committee (IRC).

Results

As of May 15, 2020, a total of 33 patients had received bintrafusp alfa, for a median of 6.0 (range, 2.0-48.1) weeks. The objective response rate was 9.1% (95% CI, 1.9%-24.3%) by IRC and investigator assessment. The median progression-free survival per IRC was 1.3 (95% CI, 1.2-1.4) months, and median overall survival was 7.7 (95% CI, 2.1-10.9) months. Twenty-five patients (75.8%) experienced treatment-related adverse events (TRAEs). Grade 3 TRAEs occurred in 5 patients (15.2%); no patients had a grade 4 TRAE. There was 1 treatment-related death (dyspnea, hemolysis, and thrombocytopenia in a patient with extensive disease at trial entry). Responses occurred independently of PD-L1 expression, and tumor RNAseq data identified HMGA2 as a potential biomarker of response.

Conclusions

Bintrafusp alfa showed clinical activity and manageable safety in patients with heavily pretreated advanced TNBC. HMGA2 was identified as a potential predictive biomarker of response.

ClinicalTrialsgov identifier

NCT02517398.

The Changing Landscape of Systemic Treatment for Cervical Cancer: Rationale for Inhibition of the TGF-β and PD-L1 Pathways

Cervical cancer is one of the most common and lethal cancers among women worldwide. Treatment options are limited in patients with persistent, recurrent, or metastatic cervical cancer, with <20% of women living >5 years. Persistent human papillomavirus (HPV) infection has been implicated in almost all cases of cervical cancer. HPV infection not only causes normal cervical cells to transform into cancer cells, but also creates an immunosuppressive environment for cancer cells to evade the immune system. Recent clinical trials of drugs targeting the PD-(L)1 pathway have demonstrated improvement in overall survival in patients with cervical cancer, but only 20% to 30% of patients show overall survival benefit beyond 2 years, and resistance to these treatments remains common. Therefore, novel treatment strategies targeting HPV infection-associated factors are currently being evaluated in clinical trials. Bintrafusp alfa is a first-in-class bifunctional fusion protein composed of the extracellular domain of the TGF-βRII receptor (a TGF-β "trap") fused to a human immunoglobulin G1 monoclonal antibody that blocks PD-L1. Early clinical trials of bintrafusp alfa have shown promising results in patients with advanced cervical cancer.

Bintrafusp alfa, a bifunctional fusion protein targeting TGF-β and PD-L1, in patients with human papillomavirus-associated malignancies

BACKGROUND

Bintrafusp alfa is a first-in-class bifunctional fusion protein composed of the extracellular domain of transforming growth factor (TGF)-βRII (a TGF-β 'trap') fused to a human IgG1 mAb blocking programmed cell death ligand 1. This is the largest analysis of patients with advanced, pretreated human papillomavirus (HPV)-associated malignancies treated with bintrafusp alfa.

METHODS

In these phase 1 (NCT02517398) and phase 2 trials (NCT03427411), 59 patients with advanced, pretreated, checkpoint inhibitor-naive HPV-associated cancers received bintrafusp alfa intravenously every 2 weeks until progressive disease, unacceptable toxicity, or withdrawal. Primary endpoint was best overall response per Response Evaluation Criteria in Solid Tumors (RECIST) V.1.1; other endpoints included safety.

RESULTS

As of April 17, 2019 (phase 1), and October 4, 2019 (phase 2), the confirmed objective response rate per RECIST V.1.1 in the checkpoint inhibitor-naive, full-analysis population was 30.5% (95% CI, 19.2% to 43.9%; five complete responses); eight patients had stable disease (disease control rate, 44.1% (95% CI, 31.2% to 57.6%)). In addition, three patients experienced a delayed partial response after initial disease progression, for a total clinical response rate of 35.6% (95% CI, 23.6% to 49.1%). An additional patient with vulvar cancer had an unconfirmed response. Forty-nine patients (83.1%) experienced treatment-related adverse events, which were grade 3/4 in 16 patients (27.1%). No treatment-related deaths occurred.

CONCLUSION

Bintrafusp alfa showed clinical activity and manageable safety and is a promising treatment in HPV-associated cancers. These findings support further investigation of bintrafusp alfa in patients with advanced, pretreated HPV-associated cancers.

Bintrafusp Alfa, a Bifunctional Fusion Protein Targeting TGF-β and PD-L1, in Patients with Esophageal Adenocarcinoma: Results from a Phase 1 Cohort

BACKGROUND

Esophageal adenocarcinoma patients have limited treatment options. TGF-β can be upregulated in esophageal adenocarcinoma, and blocking this pathway may enhance clinical response to PD-(L)1 inhibitors. Bintrafusp alfa is a first-in-class bifunctional fusion protein composed of the extracellular domain of the TGF-βRII receptor (a TGF-β "trap") fused to a human IgG1 mAb blocking PD-L1.

OBJECTIVE

The objective of this study was to investigate the efficacy and safety of bintrafusp alfa in patients with advanced, post-platinum esophageal adenocarcinoma, unselected for PD-L1 expression.

PATIENTS AND METHODS

In this phase 1 study, patients with post-platinum, PD-L1-unselected esophageal adenocarcinoma received bintrafusp alfa 1200 mg every 2 weeks until disease progression, unacceptable toxicity, or withdrawal. The primary endpoint was confirmed best overall response per RECIST 1.1 by independent review committee (IRC).

RESULTS

By the database cutoff of 24 August 2018, 30 patients (80.0% had two or more prior anticancer regimens) received bintrafusp alfa for a median of 6.1 weeks. The confirmed objective response rate (ORR) per IRC was 20.0% (95% CI 7.7-38.6); responses lasted 1.3-8.3 months. Most responses (83.3%) occurred in tumors with an immune-excluded phenotype. Investigator-assessed confirmed ORR was 13.3% (95% CI 3.8-30.7). Nineteen patients (63.3%) had treatment-related adverse events: seven patients (23.3%) had grade 3 events; no grade 4 events or treatment-related deaths occurred.

CONCLUSIONS

Bintrafusp alfa showed signs of clinical efficacy with a manageable safety profile in patients with heavily pretreated, advanced esophageal adenocarcinoma.

CLINICAL TRIALS REGISTRATION

NCT02517398.

Evaluation of bintrafusp alfa, a bifunctional fusion protein targeting TGF-β and PD-L1, in cervical cancer: Data from phase 1 and phase 2 studies

5509

Background: The accelerated FDA approval of pembrolizumab validated the efficacy of anti–PD-(L)1 therapy for pts with recurrent/metastatic cervical cancer; however, the objective response rate (ORR) with pembrolizumab was 14.3% in pts with PD-L1 expressing tumors. HPV infection is implicated in > 95% of cervical cancers and is linked to upregulation of TGF-β signaling. Bintrafusp alfa is a first-in-class bifunctional fusion protein composed of the extracellular domain of the TGF-βRII receptor (a TGF-β “trap”) fused to a human IgG1 mAb blocking PD-L1. We report pooled safety and efficacy in pts with immune checkpoint inhibitor–naive, recurrent/metastatic cervical cancer treated with bintrafusp alfa in phase 1 (INTR@PID 001; NCT02517398) and phase 2 (study 012; NCT03427411) studies. Methods: Pts with pretreated, immune checkpoint inhibitor–naive, recurrent/metastatic cervical cancer received bintrafusp alfa 0.3-30 mg/kg (phase 1 dose escalation) or 1200 mg Q2W (phase 1 expansion/phase 2) until progressive disease, unacceptable toxicity, or withdrawal. Treatment past progression was allowed. Primary endpoints were safety for the dose-escalation part of the phase 1 study and best overall response per RECIST 1.1 for the expansion part of phase 1 and phase 2 studies. Secondary endpoints for the expansion part of the phase 1 and 2 studies included safety. Results: As of May 15, 2020 (phase 1) and December 22, 2020 (phase 2), 39 pts had received bintrafusp alfa for a median duration of 2.8 months (range, 0.5-19.3). The median follow-up to data cutoff was 35.0 months and 24.1 months for the phase 1 and phase 2 studies, respectively. All pts had received prior anticancer therapy; 16 pts (41.0%) had received ≥3 prior anticancer regimens. There were 2 complete responses and 9 partial responses (PRs; ORR per RECIST 1.1, 28.2%). Median duration of response was 11.7 months (range, 1.4-41.2), and 5 pts (45.5%) had ongoing responses (duration 1.5-41.2 months). An additional delayed PR was observed (duration 23.7 months). Reponses occurred irrespective of tumor histology or prior bevacizumab or radiation treatment. Median overall survival (mOS) was 13.4 months (95% CI, 5.5 to not reached); 24-month OS rate was 33.2%. Any-grade treatment-related adverse events (TRAEs) occurred in 33 pts (84.6%). Grade 3 TRAEs occurred in 8 pts (20.5%; anemia, colitis, gastroparesis, upper gastrointestinal hemorrhage, keratoacanthoma, cystitis noninfective, hematuria, pneumonitis, rash macular [n = 1 each]); 1 patient (2.6%) had a grade 4 TRAE (asymptomatic hypokalemia related to the above grade 3 gastroparesis). No treatment-related deaths occurred. Conclusions: Bintrafusp alfa had a manageable safety profile and demonstrated clinical activity in pts with heavily pretreated, immune checkpoint inhibitor–naive recurrent/metastatic cervical cancer. Clinical trial information: NCT02517398 , NCT03427411.

Long-term follow-up of bintrafusp alfa, a bifunctional fusion protein targeting TGF-β and PD-L1, in advanced squamous cell carcinoma of the head and neck (SCCHN)

6020

Background: Bintrafusp alfa is a first-in-class bifunctional fusion protein composed of the extracellular domain of the TGF-βRII receptor (a TGF-β “trap”) fused to a human IgG1 mAb blocking PD-L1. A previous report of an expansion cohort from a phase 1 study (NCT02517398) suggested that bintrafusp alfa had a manageable safety profile and early signs of clinical activity in patients with heavily pretreated, advanced SCCHN after a median follow-up of 86.4 weeks. Here we report long-term efficacy and safety for this cohort. Methods: Patients with advanced SCCHN that progressed/recurred after platinum therapy in the recurrent/metastatic setting, or < 6 months after platinum therapy in the locally advanced setting, received bintrafusp alfa 1200 mg every 2 weeks until confirmed progressive disease, unacceptable toxicity, or trial withdrawal. The primary endpoint was confirmed best overall response assessed per RECIST 1.1 assessed by independent review committee (IRC); safety was a secondary endpoint. Results: As of May 15, 2020, 32 patients had received bintrafusp alfa for a median of 2.8 months (range, 0.5-29.9 months), no patient remained on treatment, and median follow-up to data cutoff was 41.7 months (range, 39.8-43.5 months). The objective response rate (ORR; 13%) was unchanged since the previous report; median duration of response (DOR) was increased at 21.4 months (95% CI, 5.5 months to not reached [NR]). While the clinical activity of bintrafusp alfa may be improved in patients with HPV-positive tumors (Table), outcomes were generally similar between PD-L1 subgroups (≥1% vs < 1% tumor cells). The overall safety profile was consistent with the previous report for this cohort, without grade 4 nor 5 treatment-related adverse events (TRAEs); no new TRAEs of grade 3 or that led to discontinuation of bintrafusp alfa were reported. Conclusions: With a median follow-up of over 3 years in patients with heavily pretreated advanced SCCHN, bintrafusp alfa showed sustained clinical activity and 3-year OS of 24.0%, which compares favorably to historical data. Clinical activity appeared to be greater in patients with HPV-positive tumors than those with HPV-negative tumors. The safety profile was manageable and consistent with earlier analysis. Further investigation of bintrafusp alfa in SCCHN and other HPV-associated cancers is ongoing. Clinical trial information: NCT02517398. [Table: see text]

Bintrafusp alfa (M7824), a bifunctional fusion protein targeting TGF-β and PD-L1: results from a phase I expansion cohort in patients with recurrent glioblastoma

Background

For patients with recurrent glioblastoma (rGBM), there are few options following treatment failure with radiotherapy plus temozolomide. Bintrafusp alfa is a first-in-class bifunctional fusion protein composed of the extracellular domain of the TGF-βRII receptor (a TGF-β “trap”) fused to a human IgG1 antibody blocking PD-L1.

Methods

In this phase I, open-label expansion cohort (NCT02517398), patients with rGBM that progressed after radiotherapy plus temozolomide received bintrafusp alfa 1200 mg Q2W until disease progression, unacceptable toxicity, or trial withdrawal. Response was assessed per RANO criteria. The primary endpoint was disease control rate (DCR); secondary endpoints included safety.

Results

As of August 24, 2018, 35 patients received bintrafusp alfa for a median of 1.8 (range, 0.5–20.7) months. Eight patients (22.9%) experienced disease control as assessed by an independent review committee: 2 had a partial response, 4 had stable disease, and 2 had non-complete response/non-progressive disease. Median progression-free survival (PFS) was 1.4 (95% confidence interval [CI], 1.2–1.6) months; 6- and 12-month PFS rates were 15.1% and 11.3%, respectively. Median overall survival (OS) was 5.3 (95% CI, 2.6–9.4) months; 6- and 12-month OS rates were 44.5% and 30.8%, respectively. The DCR (95% CI) was 66.7% (22.3–95.7%) for patients with IDH-mutant GBM (n = 6) and 13.8% (3.9–31.7%) for patients with IDH–wild-type GBM (n = 29). Disease control was seen regardless of PD-L1 expression. Twenty-five patients (71.4%) experienced treatment-related adverse events (grade ≥3; 17.1% [n = 6]).

Conclusions

The percentage of patients achieving disease control and the manageable safety profile may warrant further investigation of bintrafusp alfa in GBM.

Abstract OT-32-01: A phase 2, open-label study of bintrafusp alfa monotherapy in patients with HMGA2-expressing triple-negative breast cancer

Background: Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer with few targeted treatment options and a poor prognosis. Despite approvals of the anti-PD-L1 monoclonal antibody (mAb) atezolizumab in combination with nab-paclitaxel for unresectable, locally advanced/metastatic TNBC that expresses PD-L1 (tumor-infiltrating immune cells ≥1% of tumor area), many recent studies of other anti-PD-(L)1 therapies in advanced TNBC have shown limited efficacy, likely due to intrinsic therapeutic resistance. Transforming growth factor β (TGF-β), which promotes cancer progression by inducing angiogenesis, fibrosis, and epithelial-mesenchymal transition (EMT), may attenuate the efficacy of or promote resistance to anti-PD-(L)1 therapies. Bintrafusp alfa is a first-in-class bifunctional fusion protein composed of the extracellular domain of the TGF-βRII receptor (a TGF-β “trap”) fused to a human IgG1 mAb blocking PD-L1. In a cohort of 33 patients with heavily pretreated, advanced TNBC that progressed during/after first-line therapy, bintrafusp alfa was safe and resulted in antitumor activity (NCT02517398). Exploratory biomarker analysis showed that high mobility group AT-hook 2 (HMGA2) expression was 32-fold higher in tumor samples from patients who experienced disease control than from patients who had progressive disease in that cohort. Elevated expression of HMGA2, a protein associated with TGF-β signaling and a known regulator of EMT, is associated with metastasis and poor survival in breast cancer. We present the study design of a phase 2 trial to evaluate the efficacy and safety of bintrafusp alfa in patients with pretreated metastatic TNBC that expresses high levels of HMGA2. Trial Design: This phase 2, multicenter, open-label study will evaluate bintrafusp alfa monotherapy in patients with HMGA2-expressing TNBC that progressed on ≥1 line of systemic therapy for their metastatic disease. Patients will receive bintrafusp alfa 1200 mg every 2 weeks until confirmed progression, unacceptable toxicity, or trial withdrawal. Eligibility Criteria: Patients must have histologically confirmed TNBC defined by ASCO-CAP guidelines (estrogen receptor: immunohistochemistry [IHC] &lt;1%; progesterone receptor: IHC &lt;1%; human epidermal growth factor receptor 2: in situ hybridization nonamplified or IHC 0/1), high tumor HMGA2 expression, ECOG performance status ≤1, and measurable disease by RECIST 1.1. Patients must have experienced disease progression while receiving the most recent therapy prior to enrollment. HMGA2 expression will be centrally determined on archival or fresh tumor tissue by RT-PCR. Prescreening for HMGA2 expression while receiving preceding treatment is allowed; a fresh tumor biopsy prior to study entry may be requested for exploratory biomarker analysis. Patients with prior exposure to immunotherapy are not eligible. Specific Aims: The primary endpoint is independent review committee-assessed objective response rate per RECIST 1.1. Key secondary endpoints include safety, duration of response, durable response rate, progression-free survival, and overall survival. Additional exploratory biomarker characteristics will also be investigated. Statistical Methods: Descriptive statistics, including mean, median, standard deviation, and range, will be used to characterize continuous variables. Frequency counts and percentages will be used to characterize categorical variables. Accrual: Planned enrollment is 29 patients. Contact Information: Leisha A. Emens, MD, PhD Email: emensla@upmc.edu

Citation Format: Leisha A Emens, Margaret E. Gatti-Mays, Joyce O’Shaughnessy, Luc Dirix, Giovanni Faggioni, Andrea Fontana, Jerome Martin-Babau, Christoph Helwig, Alice Huang, Riham Iadevaia, Laureen S Ojalvo. A phase 2, open-label study of bintrafusp alfa monotherapy in patients with HMGA2-expressing triple-negative breast cancer [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 OT-32-01.

Abstract 1573: Association between TGF-β signaling and HMGA2, a potential biomarker for bintrafusp alfa in triple negative breast cancer

Background: Bintrafusp alfa (M7824) is a first-in-class bifunctional fusion protein composed of the extracellular domain of the TGF-βRII receptor, to function as a TGF-β “trap”, fused to a human IgG1 antibody blocking PD-L1, which has shown early evidence of clinical activity in phase 1 studies in patients with advanced solid tumors. We recently reported high expression of HMGA2 in patients with triple negative breast cancer (TNBC) who experienced disease control (response or stable disease) with bintrafusp alfa treatment compared with those who had progressive disease, suggesting that HMGA2 may predict response to bintrafusp alfa in this indication. HMGA2 is a transcriptional regulator whose expression is upregulated by TGF-β signaling and is known to be an important factor in mediating TGF-β–induced epithelial–mesenchymal transition (EMT). The purpose of this study was to evaluate the association between HMGA2 expression and TGF-β signaling in TNBC and the effect of bintrafusp alfa on HMGA2/TGF-β signaling.

Methods: The syngeneic murine 4T1 tumor model was utilized for this study because it closely mimics human stage IV TNBC, has high baseline levels of HMGA2 expression, and bintrafusp alfa directly modulates canonical TGF-β signaling and induces antitumor activity in this model.

Results: Tumors from mice treated with isotype control, anti–PD-L1, anti–PD-L1(mut)/TGF-β trap (trap control), or bintrafusp alfa were analyzed by RNAseq and both bintrafusp alfa or trap control treatment decreased HMGA2 expression relative to anti–PD-L1 or isotype control treatment. In isotype control-treated 4T1 tumors Spearman's rho correlation coefficient showed that 29% (26/89) of the TGF-β signaling-related genes significantly correlated with HMGA2 expression, indicating that there is a strong association between HMGA2 and TGF-β signaling. In bintrafusp alfa-treated tumors, the association of HMGA2 and TGF-β signaling was even stronger, with 55% (49/89) of TGF-β signaling-related genes significantly associated with HMGA2, suggesting that there is a relationship between HMGA2, TGF-β signaling, and bintrafusp alfa pharmacodynamic effects in this TNBC model. Analysis of individual TGF-β signaling-related genes from this signature showed significant correlation between HMGA2 expression and the expression of TGF-β receptors, ligands, collagen, and EMT-related genes. Furthermore, both bintrafusp alfa and trap control treatment significantly reduced expression of these HMGA2-correlated TGF-β signaling-related genes relative to anti–PD-L1 or isotype control treatment in the 4T1 model, suggesting that HMGA2 is associated with TGF-β-related signaling more strongly in the presence of TGF-β sequestration.

Conclusions: Taken together, these observations warrant further analysis of the potential link between HMGA2 and bintrafusp alfa antitumor efficacy.

Citation Format: Tsz-Lun Yeung, George Locke, Adam Lazorchak, Guozhong Qin, Huakui Yu, Jin Qi, Bo Marelli, Molly Jenkins, Alex Rolfe, Laureen S. Ojalvo, Isabelle Dussault, Yan Lan. Association between TGF-β signaling and HMGA2, a potential biomarker for bintrafusp alfa in triple negative breast cancer [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 1573.

Bintrafusp Alfa, a Bifunctional Fusion Protein Targeting TGF-β and PD-L1, in Second-Line Treatment of Patients With NSCLC: Results From an Expansion Cohort of a Phase 1 Trial

INTRODUCTION

The safety and efficacy of bintrafusp alfa, a first-in-class bifunctional fusion protein composed of the extracellular domain of the transforming growth factor β (TGF-β) receptor II (a TGF-β "trap") fused to a human immunoglobulin G1 antibody blocking programmed death-ligand 1 (PD-L1), was evaluated in patients with advanced NSCLC.

METHODS

This expansion cohort of NCT02517398, an ongoing, phase 1, open-label trial, includes 80 patients with advanced NSCLC that progressed after platinum doublet therapy or after platinum-based adjuvant or neoadjuvant treatment and those who also have not received previous immunotherapy. Patients were randomized at a one-to-one ratio to receive either bintrafusp alfa 500 mg or the recommended phase 2 dosage of 1200 mg every 2 weeks. The primary end point was the best overall response (by Response Evaluation Criteria in Solid Tumors 1.1 as adjudicated by independent review committee) and was assessed by the objective response rate (ORR).

RESULTS

A total of 80 patients were randomized to receive bintrafusp alfa 500 or 1200 mg (n = 40 each). Median follow-up was 51.9 weeks (IQR, 19.6-74.0). The ORR in all patients was 21.3% (17 of 80). The ORR was 17.5% (seven of 40) and 25.0% (10 of 40) for the 500 mg dose and the 1200 mg dose (recommended phase 2 dose), respectively. At the 1200 mg dose, patients with PD-L1-positive and PD-L1-high (≥80% expression on tumor cells) had ORRs of 36.0% (10 of 27) and 85.7% (six of seven), respectively. Treatment-related adverse events occurred in 55 of the 80 patients (69%) and were graded as greater than or equal to 3 in 23 of the 80 patients (29%). Of the 80 patients, eight (10%) had a treatment-related adverse event that led to treatment discontinuation; no treatment-related deaths occurred.

CONCLUSIONS

Bintrafusp alfa had encouraging efficacy and manageable tolerability in patients with NSCLC previously treated with platinum.

Bintrafusp alfa, a bifunctional fusion protein targeting TGF-β and PD-L1, in advanced squamous cell carcinoma of the head and neck: results from a phase I cohort

BACKGROUND

We report the clinical activity and safety of bintrafusp alfa, a first-in-class bifunctional fusion protein composed of the extracellular domain of the transforming growth factor β (TGF-β)RII receptor (a TGF-β 'trap') fused to a human IgG1 monoclonal antibody blocking programmed death-ligand 1 (PD-L1), in patients with heavily pretreated squamous cell carcinoma of the head and neck (SCCHN).

METHODS

In this phase I dose-expansion cohort, patients with advanced SCCHN not amenable to curative therapy that progressed/recurred after platinum therapy in the recurrent/metastatic setting, or <6 months after platinum therapy in the locally advanced setting, received bintrafusp alfa 1200 mg intravenously every 2 weeks. The primary endpoint was confirmed best overall response (BOR; Response Evaluation Criteria for Solid Tumors (RECIST) 1.1) per independent review committee (IRC); other endpoints included BOR per investigator and safety.

RESULTS

As of August 24, 2018, 32 patients had received bintrafusp alfa (median follow-up 86.4 weeks; range 2-97). Per IRC, the confirmed objective response rate (ORR) was 13% (95% CI 4% to 29%; 4 partial responses (PR)); 4 patients had stable disease (SD) (disease control rate 34%; 95% CI 12% to 43%). Per investigator, there were 5 PRs (ORR, 16%), including 2 patients who developed delayed PRs after initial disease increase (total clinical response rate 22%). Responses (ORRs) were observed in patients with PD-L1-positive (12%), PD-L1-negative (17%; 73-10 antibody for immunohistochemistry), human papillomavirus (HPV)-positive (33%) and HPV-negative tumors (5%). Grade 3 treatment-related adverse events (TRAEs) were reported in 11 patients (34%), with no grade 4 TRAEs or treatment-related deaths.

CONCLUSIONS

Bintrafusp alfa showed clinical activity across subgroups of PD-L1 expression and in HPV-positive tumors and had a manageable safety profile in patients with heavily pretreated advanced SCCHN. Activity in HPV-positive tumors is favorable compared with historical data from PD-L1 inhibitors and is being further investigated in an ongoing study of HPV-associated tumors.

TRIAL REGISTRATION NUMBER

NCT02517398.

Two-year follow-up of bintrafusp alfa, a bifunctional fusion protein targeting TGF-β and PD-L1, for second-line (2L) treatment of non-small cell lung cancer (NSCLC)

9558

Background: Bintrafusp alfa (M7824) is a first-in-class bifunctional fusion protein composed of the extracellular domain of the TGF-βRII receptor (a TGF-β “trap”) fused to a human IgG1 mAb blocking PD-L1. Interim analysis of a global phase 1 study (NCT02517398) found an objective response rate (ORR) of 27.5% and a manageable safety profile in patients with NSCLC who received bintrafusp alfa 1200 mg in the 2L setting; median overall survival (OS) was not reached. Here we present the longest efficacy and safety follow-up in a cohort receiving bintrafusp alfa. Methods: Patients with advanced NSCLC unselected for PD-L1 expression level who progressed after first-line standard treatment (no prior immunotherapy) were randomized to receive bintrafusp alfa 500 or 1200 mg (n = 40 each) Q2W until disease progression, unacceptable toxicity or trial withdrawal. The primary objective was best overall response (BOR) per RECIST 1.1; secondary and exploratory objectives include safety and OS, respectively. Results: As of October 15, 2019, a total of 40 patients received bintrafusp alfa at the recommended phase 2 dose of 1200 mg Q2W for a median of 17 (range, 2-136) weeks, with a median follow-up of 128 weeks; 18 patients were still alive, 3 patients had an ongoing response, and 1 patient remained on treatment. Results for the 1200 mg dose cohort showed an ORR of 27.5%, and a median duration of response of 18 months. The 18- and 24-month progression-free survival and OS rates were 18.4% and 11.0%, and 49.7% and 39.7%, respectively. Duration of response rates at 18 and 24 months were 42.4% and 21.2%, respectively. Median OS in patients with positive (≥1%) PD-L1 expression was 21.7 months; 6 of 7 patients with high (≥80% with Ab clone 73-10, which is equivalent to ≥50% with 22C3) PD-L1 expression were still alive. The overall safety profile has remained consistent since the interim analysis, with no new safety signals or deaths and 1 additional treatment-related discontinuation (blood alkaline phosphatase increased). Conclusions: After two years of follow-up, bintrafusp alfa continues to show manageable safety with durable responses and encouraging long-term survival, especially in patients with high PD-L1 expression. A study evaluating bintrafusp alfa vs pembrolizumab as first-line treatment for NSCLC is ongoing in patients with high PD-L1 expression (NCT03631706). Clinical trial information: NCT02517398 .

Selection of the Recommended Phase 2 Dose for Bintrafusp Alfa, a Bifunctional Fusion Protein Targeting TGF-β and PD-L1

Bintrafusp alfa, a first‐in‐class bifunctional fusion protein composed of the extracellular domain of the TGF‐βRII receptor (TGF‐β “trap”) fused to a human IgG1‐blocking PD‐L1, showed a manageable safety profile and clinical activity in phase I studies in patients with heavily pretreated advanced solid tumors. The recommended phase 2 dose (RP2D) was selected based on integration of modeling, simulations, and all available data. A 1,200‐mg every 2 weeks (q2w) dose was predicted to maintain serum trough concentration (C_trough) that inhibits all targets of bintrafusp alfa in circulation in > 95% of patients, and a 2,400‐mg every 3 weeks (q3w) dose was predicted to have similar C_trough. A trend toward an association between exposure and efficacy variables and a relatively stronger inverse association between clearance and efficacy variables were observed. Exposure was either weakly or not correlated with probability of adverse events. The selected intravenous RP2D of bintrafusp alfa is 1,200 mg q2w or 2,400 mg q3w.

Abstract P3-09-06: Bintrafusp alfa (M7824), a bifunctional fusion protein targeting transforming growth factor-β and programmed death ligand 1, in advanced triple-negative breast cancer: Preliminary results from a phase 1 cohort

Background: Approximately 10%-20% of breast cancers (BCs) are classified as triple-negative breast cancer (TNBC). TNBC lacks targeted treatment options and has a poor prognosis. Bintrafusp alfa (M7824) is an innovative first-in-class bifunctional fusion protein composed of the extracellular domain of the TGF-βRII receptor (a TGF-β “trap”) fused to a human IgG1 mAb blocking PD-L1. We report interim results in patients with advanced TNBC treated with bintrafusp alfa in an expansion cohort of an ongoing, open-label, phase 1 trial (NCT02517398).

Methods: Eligible patients had confirmed TNBC (ER: IHC &lt;1%; PR: IHC &lt;1%; HER2: FISH non-amplified, IHC 0/1+, or IHC 2+ and FISH non-amplified) that progressed during or after first-line chemotherapy with an ECOG performance status of ≤1 and measurable disease by RECIST 1.1. Prior treatment with immune checkpoint inhibitors was not permitted. Patients received bintrafusp alfa 1200 mg every 2 weeks until confirmed progression, unacceptable toxicity, or trial withdrawal. The primary endpoint was confirmed best overall response (BOR) as assessed by independent review committee (IRC) according to RECIST 1.1. Key secondary endpoints included investigator-assessed BOR and safety. Exploratory endpoints included an extensive integrated biomarker evaluation of patient samples. These data are presented in a separate, submitted abstract.

Results: As of August 24, 2018, 33 patients with heavily pretreated TNBC (54.5% of patients had ≥4 prior regimens) were enrolled in this study of bintrafusp alfa. Patients received a median of 3 doses of bintrafusp alfa (range, 1-24). Confirmed responses as assessed by IRC and investigator occurred in 3 patients (1 complete response and 2 partial responses as assessed by IRC; ORR, 9.1% [95% CI, 1.9%-24.3%]); disease control was achieved in a total of 5 patients (15.2% [95% CI, 5.1%-31.9%]) by both IRC and investigator read. The median progression-free survival per IRC was 1.3 months (95% CI, 1.2-1.4 months), and the median overall survival was 7.8 months (95% CI, 2.1-12.8 months). Importantly, a biomarker related to TGF-β biology was identified via RNAseq analysis of tumor samples with 32.0-fold higher expression in patients who experienced disease control (response or stable disease) compared with those who had progressive disease (biomarker results for this expansion cohort are presented in a separate abstract). PD-L1 expression was not associated with response to treatment. In the entire cohort, 6 patients (18.2%) experienced ≥1 grade 3 treatment-related adverse event (TRAE), including anemia (n=3), asthenia, decreased appetite, generalized rash, hypophysitis, and increased transaminases (all n=1). No grade 4 TRAEs were reported. Three patients discontinued treatment due to TRAEs, including 1 death that was assessed by the investigator as related to treatment. Dyspnea, hemolysis, and thrombocytopenia were reported as grade 5 TRAEs in this patient, who had extensive disease at trial entry and was noted to have multiple pulmonary emboli, progressive disease, and expanding pleural effusion after 3 doses. No autoantibodies mediating hemolysis or thrombocytopenia were identified on workup.

Conclusions: In summary, bintrafusp alfa was well tolerated, with a safety profile consistent with expectations in this heavily pretreated, advanced TNBC cohort. We identified high expression of a potential predictive biomarker of response in patients with advanced TNBC treated with bintrafusp alfa. Detailed biomarker data are presented in the separate abstract and warrant further investigation of bintrafusp alfa in TNBC.

Citation Format: Alexander Spira, Ahmad Awada, Nicolas Isambert, David Lorente Estellés, John Nemunaitis, Nicolas Penel, Laureen S Ojalvo, Christoph Helwig, Christian Borel. Bintrafusp alfa (M7824), a bifunctional fusion protein targeting transforming growth factor-β and programmed death ligand 1, in advanced triple-negative breast cancer: Preliminary results from a phase 1 cohort [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 P3-09-06.

Abstract P3-09-13: Identification of a tumor biomarker in advanced triple-negative breast cancer that predicts response to bintrafusp alfa (M7824), a bifunctional fusion protein targeting transforming growth factor-β and programmed death ligand 1

Background: Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer. Identification of biomarkers that are predictive of response to investigational therapies will help identify patients that are more likely to clinically benefit from treatment. Bintrafusp alfa (M7824) is an innovative first-in-class bifunctional fusion protein composed of the extracellular domain of the TGF-βRII receptor (a TGF-β “trap”) fused to a human IgG1 mAb blocking PD-L1. In this expansion cohort of a global, phase 1, open-label trial (NCT02517398), an extensive tumor biomarker analysis was conducted to identify potential markers correlating with efficacy in patients with advanced TNBC treated with bintrafusp alfa.

Methods: Patients received infusions of bintrafusp alfa 1200 mg every 2 weeks until confirmed progression, unacceptable toxicity, or trial withdrawal. Tumor archival material was collected from each patient for biomarker analysis. All biomarker analyses were exploratory. PD-L1 expression and immune phenotype were determined by immunohistochemistry. Tumor samples were also processed for RNA sequencing (RNAseq) and resulting data were analyzed to identify potential associations between gene expression and efficacy of bintrafusp alfa treatment.

Results: As of August 24, 2018, 33 patients with heavily pretreated TNBC were treated with bintrafusp alfa (54.5% of patients received ≥4 prior regimens). The objective response rate was 9.1% (n=3) and the disease control rate was 15.2% in a total of 5 patients. PD-L1 expression levels in tumor cells and in the tumor microenvironment were generally low in this cohort with the majority of patients having 0% PD-L1+ tumor cells and/or ≤10% PD-L1+ immune cells in their tumor microenvironment. Moreover, several patients had an immune desert phenotype. PD-L1 expression was not associated with response to treatment. Importantly, exploratory analysis of RNAseq data (n=26 passing quality control) identified differential expression of the high mobility group AT-hook 2 (HMGA2) gene with 32.0-fold higher expression (as computed by DESeq2; q=2.23e−13) in patients who experienced disease control (response or stable disease) compared to those who had progressive disease. HMGA2 is a transcriptional regulator whose expression is upregulated by TGF-β signaling. Furthermore, HMGA2 is known to be an important factor in mediating TGF-β-induced epithelial-mesenchymal transition. In The Cancer Genome Atlas dataset, approximately 12% of subjects annotated as TNBC have high expression of HMGA2. Clinical efficacy and safety data for this expansion cohort are presented in a separate abstract.

Conclusions: We identified high expression of HMGA2 as a potential predictive biomarker of response in TNBC patients treated with bintrafusp alfa. HMGA2 assay development is on-going to confirm this finding in a future clinical trial.

Citation Format: George Locke, Yue Zhang, Laureen S Ojalvo, Christoph Helwig, Alex Rolfe, Olaf Christensen, Isabelle Dussault. Identification of a tumor biomarker in advanced triple-negative breast cancer that predicts response to bintrafusp alfa (M7824), a bifunctional fusion protein targeting transforming growth factor-β and programmed death ligand 1 [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 P3-09-13.

Randomized open-label study of M7824 versus pembrolizumab as first-line (1L) treatment in patients with PD-L1 expressing advanced non-small cell lung cancer (NSCLC)

TPS9114

Background: Transforming growth factor β (TGF- β) promotes tumor progression via immune- and non–immune-related processes. M7824 is an innovative first-in-class bifunctional fusion protein composed of 2 extracellular domains of TGF-βRII (a TGF-β “trap”) fused to a human IgG1 monoclonal antibody against PD-L1. Targeting these independent and complementary pathways may restore and enhance antitumor responses. An expansion cohort of the NCT02517398 study of patients with advanced NSCLC (n = 80) treated with M7824 in the second-line setting presented at ESMO 2018 showed an objective response rate of 86% in the subgroup with high PD-L1 tumor expression at the recommended phase 2 dose (1200 mg intravenously [IV] every 2 weeks [Q2W]). Observed data support the hypothesis that M7824 may be superior to other PD-(L)1 inhibitors, including pembrolizumab, for the treatment of NSCLC. Based on the promising antitumor activity and manageable safety profile, this study will evaluate M7824 treatment in patients with advanced NSCLC in the 1L setting. Methods: Here we present a global, randomized trial comparing M7824 vs pembrolizumab in the 1L treatment of patients with metastatic NSCLC with high PD-L1 expression levels. Patients in this study must have a histologically confirmed diagnosis of advanced NSCLC with high PD-L1 expression on tumor cells (defined as either ≥80% by the Dako 73-10 pharmDx kit or ≥50% by the Dako 22C3 pharmDx kit since both assays are expected to select a similar patient population at their respective cut-offs). ECOG performance status must be 0 or 1. Patients must not have received prior systemic treatment for advanced NSCLC. Patients with tumors with actionable mutations (for which targeted therapy is locally approved) are not eligible. Patients will receive 1200 mg Q2W or pembrolizumab 200 mg Q3W as an IV infusion until confirmed disease progression, unacceptable toxicity, or trial withdrawal. Dual primary endpoints are progression-free survival and best overall response; key secondary endpoints include overall survival, duration of response, and safety. Estimated enrollment is 300 patients. Clinical trial information: NCT03631706.

Randomized open-label study of M7824 versus pembrolizumab as first-line (1L) treatment in patients with PD-L1 expressing advanced non-small cell lung cancer (NSCLC)

TPS127

Background: Transforming growth factor β (TGF- β) promotes tumor progression via immune- and non–immune-related processes. M7824 is an innovative first-in-class bifunctional fusion protein composed of 2 extracellular domains of TGF-βRII (a TGF-β “trap”) fused to a human IgG1 monoclonal antibody against PD-L1. Targeting these independent and complementary pathways may restore and enhance antitumor responses. An expansion cohort of the study of patients with advanced NSCLC (n=80) treated with M7824 in the second-line setting presented at ESMO 2018 showed an objective response rate of 86% in the subgroup with high PD-L1 tumor expression at the recommended phase 2 dose (1200 mg intravenously [IV] every 2 weeks [Q2W]). Observed data support the hypothesis that M7824 may be superior to other PD-(L)1 inhibitors, including pembrolizumab, for the treatment of NSCLC. Based on the promising antitumor activity and manageable safety profile, this study will evaluate M7824 treatment in patients with advanced NSCLC in the 1L setting. Methods: Here we present a global, randomized trial comparing M7824 vs pembrolizumab in the 1L treatment of patients with metastatic NSCLC with high PD-L1 expression levels. Patients in this study must have a histologically confirmed diagnosis of advanced NSCLC with high PD-L1 expression on tumor cells (defined as either ≥80% by the Dako 73-10 pharmDx kit or ≥50% by the Dako 22C3 pharmDx kit since both assays are expected to select a similar patient population at their respective cut-offs). ECOG performance status must be 0 or 1. Patients must not have received prior systemic treatment for advanced NSCLC. Patients with tumors with actionable mutations (for which targeted therapy is locally approved) are not eligible. Patients will receive 1200 mg Q2W or pembrolizumab 200 mg Q3W as an IV infusion until confirmed disease progression, unacceptable toxicity, or trial withdrawal. Dual primary endpoints are progression-free survival and best overall response; key secondary endpoints include overall survival, duration of response, and safety. Estimated enrollment is 300 patients. Clinical trial information: NCT02517398, NCT03631706 .

Tumor-associated macrophages and the tumor immune microenvironment of primary and recurrent epithelial ovarian cancer

Tumor-infiltrating lymphocytes (TILs) are associated with better prognosis in newly diagnosed epithelial ovarian cancer (EOC), but clinical trials of immunotherapies in patients with heavily treated disease reveal limited activity. Understanding the tumor microenvironment (TME) of primary and recurrent EOC should guide future trials. Here, we evaluated the TME of paired primary and recurrent tumors (n = 17), and non-paired primary (n = 20) and recurrent (n = 15) tumors, for CD8+ T cells, FOXP3+ regulatory T cells (Tregs), CD68+ tumor-associated macrophages (TAMs), programmed cell death protein 1 (PD-1) and programmed cell death ligand 1 (PD-L1). CD8+ T cells were similar in primary and recurrent tumors, but Tregs were higher in recurrent tumors (P = .0210). Higher TAM density (≥5%) associated with higher Tregs (P = .001) and CD8+ T cells (P < .001) in recurrent tumors, but only with higher Tregs in primary tumors (P = .02). TAM-dense recurrent tumors expressed PD-L1 on tumor and immune cells, whereas TAM-dense primary tumors expressed PD-L1 predominantly on immune cells. In survival analyses, higher Tregs in primary tumors correlated with decreased time to first recurrence (17.0 versus 28.5 months, P = .022). Conversely, higher Tregs in recurrent tumors correlated with longer overall survival (OS) from recurrence (median not met versus 20.0 months, P = .022). TAM density did not affect patient survival. However, patients with increased TAMs at recurrence (n = 5) had longer OS from recurrence compared to patients without increased TAMs (n = 12) (56.0 versus 20.0 months); with the small sample size, this did not reach statistical significance (P = .074). Further characterization of the evolution of the TME is warranted.

Abstract 3991: Profiling the immune tumor microenvironment in primary and recurrent epithelial ovarian cancer

Clinical trials targeting the immune tumor microenvironment (TME) in epithelial ovarian cancer (EOC) typically have included patients with heavily pre-treated advanced disease and demonstrated only marginal efficacy. A better understanding of how the EOC TME evolves with progression from primary to recurrent disease may inform future immunotherapy trials. Here, we evaluate the immune TME in primary and recurrent EOC using tissue microarrays. Our cohort included matched primary and recurrent tumors from 17 patients, and additional non-matched primary tumors from 20 patients and recurrent tumors from 15 patients. We stained for CD8, FOXP3 (regulatory T cells (Tregs)), CD68 (tumor associated macrophages (TAMs)), programmed cell death protein 1 (PD-1) and programmed death ligand 1 (PD-L1) by immunohistochemistry to interrogate the immune composition of the TME. Tregs increased in recurrent tumors compared to primary tumors (8.0 vs 14.2/HPF, p=0.0210). Higher TAM density was associated with higher levels of Treg and CD8+ T cell infiltrates in recurrent tumors (p=0.001 and p&lt;0.001, respectively), and with higher Treg but not CD8+ T cell infiltrates in primary tumors (p=0.027 and p=0.200). TAM-dense recurrent tumors had increased PD-L1 on tumor cells and immune cells, whereas TAM-dense primary tumors had increased PD-L1 only on immune cells. Increased Tregs in primary tumors correlated with decreased time to first recurrence (17.0 vs 28.5 months, p=0.022). Conversely, increased Tregs in recurrent tumors correlated with longer overall survival (OS) from recurrence (median not met vs 20.0m, p=0.022). Although TAM density did not affect patient survival, analysis of matched primary and recurrent tumors revealed that patients with increased TAMs at recurrence (n=5) had a longer median OS from recurrence than patients without increased TAMs at recurrence (n=12). Tregs increased at recurrence in the majority of matched tumor pairs (n=12), but there was no correlation with survival. In conclusion, the TME of EOC is immunologically active. TAM-dense recurrent disease had higher CD8+ T cell and Treg infiltrates and PD-L1 expression. In this study, patients with increased cellular recruitment to the TME at recurrence had improved survival. Larger, more detailed studies characterizing the evolution of the TME with progression from primary EOC to recurrence are warranted.

Citation Format: Laureen S. Ojalvo, Elizabeth D. Thompson, Tian-Li Wang, Alan K. Meeker, Ie-Ming Shih, Amanda N. Fader, Ashley Cimino-Mathews, Leisha A. Emens. Profiling the immune tumor microenvironment in primary and recurrent epithelial ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3991. doi:10.1158/1538-7445.AM2017-3991

A STING Agonist Given with OX40 Receptor and PD-L1 Modulators Primes Immunity and Reduces Tumor Growth in Tolerized Mice

Stimulator of interferon genes (STING) signaling induces IFNβ production by intratumoral dendritic cells (DC), driving T-cell priming and recruitment into the tumor microenvironment (TME). We examined to what extent preexisting antigen-specific tolerance influenced the efficacy of in situ delivery of a potent STING-activating cyclic dinucleotide (CDN), ADU S-100, against established HER-2⁺ breast tumors. ADU S-100 induced HER-2-specific CD8⁺ T-cell priming and durable tumor clearance in 100% of nontolerant parental FVB/N mice. In contrast, ADU S-100 did not sufficiently prime HER-2-specific CD8⁺ T cells in tolerant neu/N mice, resulting in only delayed tumor growth and tumor clearance in 10% of the mice. No differences in IFNβ production, DC priming, or HER-2-specific CD8⁺ T-cell trafficking were detected between FVB/N and neu/N mice. However, activation and expansion of HER-2-specific CD8⁺ T cells were defective in neu/N mice. Immune cell infiltrates of untreated tumor-bearing neu/N mice expressed high numbers of PD1 and OX40 receptors on their CD8⁺ T cells, and PD-L1 was highly expressed on both myeloid and tumor cells. Modulating PD-L1 and OX40 receptor signaling combined with intratumoral ADU S-100 administration enhanced HER-2-specific CD8⁺ T-cell activity, clearing tumors in 40% of neu/N mice. Thus, intratumoral STING agonists could potently prime tumor antigen-specific CD8⁺ T-cell responses, and adding PD-L1 blockade and OX40 receptor activation can overcome antigen-enforced immune tolerance to induce tumor regression. Cancer Immunol Res; 5(6); 468-79. ©2017 AACR.

Emerging immunotherapies in ovarian cancer

Despite a global effort to significantly reduce mortality, ovarian cancer remains the fifth leading cause of cancer death among American women, and five-year survival rates remain discouragingly low at 45%. Novel therapies are urgently needed. Notably, higher infiltration of activated immune cells into the tumor microenvironment correlates with improved ovarian cancer survival, suggesting that promoting their activity could favorably impact clinical outcomes. Immunotherapy has recently demonstrated impressive clinical benefit in a variety of solid tumors. Immunotherapy strategies tested in ovarian cancer include vaccines, adoptive T cell therapy, and immune checkpoint blockade. Ultimately, a combination immunotherapy approach that integrates immunotherapy with other cancer treatment modalities in additive or synergistic ways will most effectively improve survival.

Gene expression analysis of macrophages that facilitate tumor invasion supports a role for Wnt-signaling in mediating their activity in primary mammary tumors

The tumor microenvironment modifies the malignancy of tumors. In solid tumors, this environment is populated by many macrophages that, in genetic studies that depleted these cells from mouse models of breast cancer, were shown to promote tumor progression to malignancy and increase metastatic potential. Mechanistic studies showed that these tumor-promoting effects of macrophages are through the stimulation of tumor cell migration, invasion, intravasation, and enhancement of angiogenesis. Using an in vivo invasion assay, it was demonstrated that invasive carcinoma cells are a unique subpopulation of tumor cells whose invasion and chemotaxis is dependent on the comigration of tumor-associated macrophages (TAMs) with obligate reciprocal signaling through an epidermal growth factor-CSF-1 paracrine loop. In this study, these invasion-promoting macrophages were isolated and subjected to analysis of their transcriptome in comparison with TAMs isolated indiscriminately to function using established macrophage markers. Unsupervised analysis of transcript patterns showed that the invasion-associated TAMs represent a unique subpopulation of TAMs that, by gene ontology criteria, have gene expression patterns related to tissue and organ development. Gene set enrichment analysis showed that these macrophages are also specifically enriched for molecules involved in Wnt-signaling. Previously, it was shown that macrophage-derived Wnt molecules promote vascular remodeling and that tumor cells are highly motile and intravasate around perivascular TAM clusters. Taken together, we conjecture that invasive TAMs link angiogenesis and tumor invasion and that Wnt-signaling plays a role in mediating their activity.

High-density gene expression analysis of tumor-associated macrophages from mouse mammary tumors

Clinical and experimental evidence indicates that tumor-associated macrophages (TAMs) promote malignant progression. In breast cancer, TAMs enhance tumor angiogenesis, tumor cell invasion, matrix remodeling, and immune suppression against the tumor. In this study, we examined late-stage mammary tumors from a transgenic mouse model of breast cancer. We used flow cytometry under conditions that minimized gene expression changes to isolate a rigorously defined TAM population previously shown to be associated with invasive carcinoma cells. The gene expression signature of this population was compared with a similar population derived from spleens of non-tumor-bearing mice using high-density oligonucleotide arrays. Using stringent selection criteria, transcript abundance of 460 genes was shown to be differentially regulated between the two populations. Bioinformatic analyses of known functions of these genes indicated that formerly ascribed TAM functions, including suppression of immune activation and matrix remodeling, as well as multiple mediators of tumor angiogenesis, were elevated in TAMs. Further bioinformatic analyses confirmed that a pure and valid TAM gene expression signature in mouse tumors could be used to assess expression of TAMs in human breast cancer. The data derived from these more physiologically relevant autochthonous tumors compared with previous studies in tumor xenografts suggest tactics by which TAMs may regulate tumor angiogenesis and thus provide a basis for exploring other transcriptional mediators of TAM trophic functions within the tumor microenvironment.

Induction of an embryonic globin gene promoter by short-chain fatty acids

Short-chain fatty acids (SCFAs) and dimethyl sulfoxide (DMSO) induce adult erythroid differentiation in murine erythroleukemia (MEL) cells, but only SCFAs concurrently up-regulate expression from the endogenous embryonic globin gene epsilony. The epsilony promoter, linked to a reporter gene and stably transfected into MEL cells, was tested during adult erythroid differentiation. Both the epsilony-CACCC site at -114 bp and enhancer sequences (hypersensitive site 2 [HS2]) from the beta-globin locus control region (LCR) were essential to maximal SCFA-mediated induction of expression from these constructs in MEL cells. Gel-shift analyses of binding activity from SCFA-induced MEL cell nuclear extracts showed in vitro binding by specificity proteins 1 and 3 (SP1, SP3) and basic or erythroid Krüppel-like factors (BKLF, EKLF) at the epsilony-CACCC site. In a functional analysis, transient cotransfections in nonerythroid NIH/3T3 cells of SP1, SP3, BKLF, or EKLF and HS2 epsilony promoter-luciferase constructs, with or without coactivators (p300, CREB-binding protein [CBP], or p300/CBP-associated factor [PCAF]) and SCFAs, were performed. SP1, SP3, and EKLF further increased expression from HS2 epsilony promoter constructs following exposure to SCFAs. This effect was variably augmented by coactivators and was diminished in EKLF mutants that were unable to undergo histone/factor-acetyl transferase (H/FAT)-mediated acetylation. In addition, acetylation of SP1 was detectable in NIH/3T3 cells following exposure to SCFAs. In sum, LCR sequence and an embryonic globin gene promoter CACCC site were essential to that promoter's up-regulation during SCFA-mediated induction of adult erythroid differentiation in vitro. Of factors that interact at the CACCC site, SCFA-mediated acetylation is implicated in SP1 and EKLF, and may be a mechanism through which SCFAs induce embryonic/fetal globin gene promoters during adult erythroid differentiation.