Bispecific antibodies and CAR-T cells: dueling immunotherapies for large B-cell lymphomas

Despite recent advances in frontline therapy for diffuse large B-cell lymphoma (DLBCL), at least a third of those diagnosed still will require second or further lines for relapsed or refractory (rel/ref) disease. A small minority of these can be cured with standard chemoimmunotherapy/stem-cell transplant salvage approaches. CD19-directed chimeric antigen receptor T-cell (CAR-19) therapies are increasingly altering the prognostic landscape for rel/ref patients with DLBCL and related aggressive B-cell non-Hodgkin lymphomas. Long-term follow up data show ongoing disease-free outcomes consistent with cure in 30-40% after CAR-19, including high-risk patients primary refractory to or relapsing within 1 year of frontline treatment. This has made CAR-19 a preferred option for these difficult-to-treat populations. Widespread adoption, however, remains challenged by logistical and patient-related hurdles, including a requirement for certified tertiary care centers concentrated in urban centers, production times of at least 3-4 weeks, and high per-patients costs similar to allogeneic bone-marrow transplantation. Bispecific antibodies (BsAbs) are molecular biotherapies designed to bind and activate effector T-cells and drive them to B-cell antigens, leading to a similar cellular-dependent cytotoxicity as CAR-19. May and June of 2023 saw initial approvals of next-generation BsAbs glofitamab and epcoritamab in DLBCL as third or higher-line therapy, or for patients ineligible for CAR-19. BsAbs have similar spectrum but generally reduced severity of immune related side effects as CAR-19 and can be administered in community settings without need to manufacture patient-specific cellular products. To date and in contrast to CAR-19, however, there is no convincing evidence of cure after BsAbs monotherapy, though follow up is limited. The role of BsAbs in DLBCL treatment is rapidly evolving with trials investigating use in both relapsed and frontline curative-intent combinations. The future of DLBCL treatment is bound increasingly to include effector cell mediated immunotherapies, but further optimization of both cellular and BsAb approaches is needed.

Adjuvant enzalutamide for the treatment of early-stage androgen-receptor positive, triple-negative breast cancer: a feasibility study

PURPOSE

Chemotherapy with or without immunotherapy remains the mainstay of treatment for triple-negative breast cancer (TNBC). A subset of TNBCs express the androgen receptor (AR), representing a potential new therapeutic target. This study assessed the feasibility of adjuvant enzalutamide, an AR antagonist, in early-stage, AR-positive (AR +) TNBC.

METHODS

This study was a single-arm, open-label, multicenter trial in which patients with stage I-III, AR ≥ 1% TNBC who had completed standard-of-care therapy were treated with enzalutamide 160 mg/day orally for 1 year. The primary objective of this study was to evaluate the feasibility of 1 year of adjuvant enzalutamide, defined as the treatment discontinuation rate of enzalutamide due to toxicity, withdrawal of consent, or other events related to tolerability. Secondary endpoints included disease-free survival (DFS), overall survival (OS), safety, and genomic features of recurrent tumors.

RESULTS

Fifty patients were enrolled in this study. Thirty-five patients completed 1 year of therapy, thereby meeting the prespecified trial endpoint for feasibility. Thirty-two patients elected to continue with an optional second year of treatment. Grade ≥ 3 treatment-related adverse events were uncommon. The 1-year, 2-year, and 3-year DFS were 94%, 92% , and 80%, respectively. Median OS has not been reached.

CONCLUSION

This clinical trial demonstrates that adjuvant enzalutamide is a feasible and well-tolerated regimen in patients with an early-stage AR + TNBC. Randomized trials in the metastatic setting may inform patient selection through biomarker development; longer follow-up is needed to determine the effect of anti-androgens on DFS and OS in this patient population.

Pan-cancer association between increased iron utilization and poor prognosis highlights potential of transferrin receptor-targeting therapies in multiple tumor types

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Background: The cell-surface transferrin receptor TFR1 imports iron-bound transferrin into cells via clathrin-mediated endocytosis. Tumors require constitutive iron import to drive proliferation, and several studies establish TFR1 as a target able to facilitate intracellular delivery of cytotoxic therapeutic molecules. Our own work previously revealed association between high expression of TFRC, the gene encoding TFR1, and high risk for poor outcome in diffuse large B-cell lymphoma (DLBCL). We showed therapetuic targeting of TFR1 in DLBCL results in significant anti-tumor benefit. Systematic analysis of TFRC expression as a prognostic marker across tumor types, however, has not been investigated. Methods: Tissue samples underwent comprehensive molecular profiling at Caris Life Sciences. Analyses included next generation sequencing of DNA (592 Gene Panel, NextSeq, or whole exome sequencing, NovaSeq), RNA (NovaSeq, whole transcriptome sequencing, WTS) and immunohistochemistry. Overall survival (OS) was calculated from date of tissue collection to last contact from insurance claims data and employed Kaplan-Meier analysis by Wilcoxon statistics, with p < 0.05 defined as significant. Results: Amongst 47 cancer types included, colorectal cancer (CRC) displayed the highest level of TFRC mRNA, followed by gastric cancer. In an all-tumor cohort (n = 93248), patients with higher TFRC expression (cutoff = median) had significantly worse OS (HR = 1.348, 95% CI [1.317-1.38], p < 0.00001). This was statistically significant in 23 individual tumor types. Drilling down further, TFRC adverse prognostic value was mainly driven by cohorts with larger number of samples in the database, including non-small cell lung cancer (n = 17309), CRC (n = 12860), breast cancer (n = 8632), ovarian carcinoma (n = 7998), uterine neoplasms (n = 6097), prostate adenocarcinoma (n = 3411), glioblastoma (n = 2821), gastric cancer (n = 1579), and others. Surprisingly, TFRC overexpression correlated with improved outcome in vulvar squamous cell carcinoma (VSCC, n = 297). TFRC was found to be most prognostic in prostate adenocarcinoma with median OS 1139 days in pts with high vs 3230 days in pts with low TFRC (HR = 2.556, 95% CI [2.213-2.951], p < 0.00001). Conclusions: Our study is the first to combine modern molecular profiling with a large cohort of clinical tissue samples to reveal a prognostic role for TFRC expression in a variety of solid tumor types. We found TFRC overexpression to be prognostic in a large proportion of histologies, though surprisingly association with improved OS in VSCC. Highest expression occured in CRC and gastric cancer, diseases with needs for new therapies. A number of TFR1-targeting therapeutics are currently at various stages of development, and warrant further investigation in disease cohorts identified from our study.

Abstract P1-14-03: Adjuvant enzalutamide for the treatment of early-stage androgen-receptor positive, triple negative breast cancer: A feasibility study

Background: Chemotherapy remains the mainstay of treatment for early-stage triple negative breast cancer (TNBC), yet targetable drivers of interest are under investigation. A subset of TNBCs express the androgen receptor (AR) and exhibit androgen-dependent growth. The AR-antagonist enzalutamide (ENZA) has shown activity in patients with metastatic AR+ TNBC. In this study, the feasibility of adjuvant ENZA in early-stage, AR+ TNBC was assessed (NCT02750358). As reported previously, this study met its primary endpoint of feasibility (Traina et al., ASCO 2019). Here we report secondary survival endpoints. Methods: In this single-arm, open-label, multi-center trial, patients with stage I-III, AR≥1% TNBC (ER/PR &lt;1%, HER2 negative) who had completed standard of care therapy were treated with ENZA 160 mg/day orally for 1 year. Patients who completed 1 year had an option to remain on adjuvant ENZA for another year. Toxicity was graded using National Cancer Institute Common Toxicity Criteria (NCI CTCAE) v4. The primary endpoint of this study was to evaluate feasibility of adjuvant ENZA, defined as the discontinuation rate due to toxicity, withdrawal of consent, other events related to tolerability or patient preference. The study was designed to discriminate between feasibility rates of 50% and 70% and was considered feasible if ≥29 out of 46 patients received ENZA for one year without discontinuation. Secondary endpoints included DFS, OS, safety, patient reported outcomes and correlative science. Patients who had disease progression (PD) during year 1 of ENZA without treatment discontinuation due to the above reasons were not included in the primary feasibility analysis but were included in secondary endpoint analyses for survival. Results: 50 patients enrolled on study from 05/2016 - 06/2018. The median age was 58 years (range 34-81 years); 8% had a germline BRCA1/2 (n=3) or PALB2 (n=1) mutation. 38% had stage I disease at diagnosis, 48% stage II and 14% stage III. 74% had grade 3 tumors. 94% of all patients received prior systemic chemotherapy, 81% of whom received prior anthracycline-taxane. 38% (n=19) were treated with prior neoadjuvant chemotherapy and 32% of those patients (n=6) achieved a pCR. Of those who did not achieve a pCR, 69% received adjuvant capecitabine. 47 patients were evaluable for the study endpoint and 35 patients completed 1 year of ENZA thereby meeting the prespecified trial endpoint for feasibility. 32 patients elected to continue into a second year of treatment. After a median follow-up of 140 weeks (range 4 - 236 weeks), 8 patients had a DFS event: 7 TNBC recurrences and 1 new primary breast cancer. The 1-year DFS was 94% (95% CI: 87 - 100%), 2-year DFS was 92% (95% CI: 84 - 99.8%) and the 3-year DFS was 80% (95% CI: 67 - 94%). The median DFS and OS have not yet been reached. Two patients died of TNBC recurrence after 55 and 59 weeks. There were no new or unexpected toxicities observed at study completion. Conclusion: This single-arm trial previously met its primary endpoint of feasibility in patients with early-stage AR+ TNBC. In this relatively high-risk, albeit highly selected patient population, the 3-year DFS measured 80% (95% CI: 67 - 94%) with an adjuvant endocrine therapy approach. Efforts to determine the optimal biomarker for AR+ TNBC are ongoing, so that patients most likely to respond to AR-antagonists in both the early and metastatic setting may be identified. Biomarker data from this study including PD-L1 status and tumor sequencing will be reported at the time of presentation.Funding and drug support for this study was provided by Astellas Pharma Global Development Inc./Pfizer Inc.

Citation Format: Elaine M Walsh, Ayca Gucalp, Sujata Patil, Marcia Edelweiss, Dara S Ross, Pedram Razavi, Shanu Modi, Neil M Iyengar, Rachel Sanford, Tiffany Troso-Sandoval, Mila Gorsky, Jackie Bromberg, Pamela Drullinsky, Diana Lake, Serena Wong, Patricia DeFusco, Nicholas Lamparella, Ranja Gupta, Tasmila Tabassum, Leigh Ann Boyle, Artavazd Arumov, Tiffany A Traina. Adjuvant enzalutamide for the treatment of early-stage androgen-receptor positive, triple negative breast cancer: A feasibility study [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 P1-14-03.

Proteomics reveal cap-dependent translation inhibitors remodel the translation machinery and translatome

Tactical disruption of protein synthesis is an attractive therapeutic strategy, with the first-in-class eIF4A-targeting compound zotatifin in clinical evaluation for cancer and COVID-19. The full cellular impact and mechanisms of these potent molecules are undefined at a proteomic level. Here, we report mass spectrometry analysis of translational reprogramming by rocaglates, cap-dependent initiation disruptors that include zotatifin. We find effects to be far more complex than simple “translational inhibition” as currently defined. Translatome analysis by TMT-pSILAC (tandem mass tag-pulse stable isotope labeling with amino acids in cell culture mass spectrometry) reveals myriad upregulated proteins that drive hitherto unrecognized cytotoxic mechanisms, including GEF-H1-mediated anti-survival RHOA/JNK activation. Surprisingly, these responses are not replicated by eIF4A silencing, indicating a broader translational adaptation than currently understood. Translation machinery analysis by MATRIX (mass spectrometry analysis of active translation factors using ribosome density fractionation and isotopic labeling experiments) identifies rocaglate-specific dependence on specific translation factors including eEF1ε1 that drive translatome remodeling. Our proteome-level interrogation reveals that the complete cellular response to these historical “translation inhibitors” is mediated by comprehensive translational landscape remodeling.

Tactical protein synthesis inhibition is actively pursued as a cancer therapy that bypasses signaling redundancies limiting current strategies. Ho et al. show that rocaglates, first identified as inhibitors of eIF4A activity, globally reprogram cellular translation at both protein synthesis machinery and translatome levels, inducing cytotoxicity through anti-survival GEF-H1/RHOA/JNK signaling.

Potency Meets Precision in Nano-optimized Chemotherapeutics

Chemotherapy remains the most widely used cancer treatment modality. Nanotechnology provides exciting opportunities to improve these drugs, transforming decades-old generic treatments into precise new medicines. We illustrate the potential of recent advances in nanotechnology-enhanced therapy focusing on diffuse large B-cell lymphoma (DLBCL); the most common hematologic malignancy.

Abstract 1031: Translatome and protein synthesis machinery remodeling by rocaglates drives antitumor activity

Rocaglates are under active development for cancer therapy, with the first-in-class member zotatifin recently entering Phase I/II clinical trial for advanced solid tumor malignancies (NCT04092673). Initiation of this trial was based purely on rocaglates' inhibitory activity against translation initiation factor and RNA helicase eIF4A. Rapid development of these compounds towards clinical use urgently requires a complete understanding of their mechanisms. Critically, however, the full effects of rocaglates on protein synthesis are unknown, especially with regards to up-regulated proteins and rocaglate-activated translation factors that mediate their potent anticancer activity. Past rocaglate studies focused exclusively on mechanisms and targets of translational inhibition, relying exclusively on indirect RNA-based approaches that do not reliably capture proteome-level changes, a caveat proven in cancer cells responding to drugs. Formal proteomic investigations of rocaglate effects are non-existent in the literature. We addressed these vital knowledge gaps in this study. An original proteome-level analysis using metabolic pulse-labeling and TMT-mass spectrometry revealed extensive rocaglate-induced changes in protein output (translatome), including myriad rocaglate-up-regulated proteins that drive cytotoxicity through currently uncharacterized mechanisms. Specifically, we find in vitro and in vivo that rocaglates, including zotatifin, induce GEF-H1, activating anti-survival RHOA/JNK signaling. Intriguingly, these responses occur regardless of eIF4A expression. Beyond translatome remodeling, mass spectrometry-based MATRIX interrogation of the protein synthesis machinery revealed widespread rocaglate-dependent changes. As a prime example, rocaglate-augmented eEF1ϵ1 activity mediates initiator methionine-tRNAiMet delivery to drive synthesis of rocaglate-inducible proteins and phenotypes. Overall, this study transforms the current definition of rocaglates from one-dimensional eIF4A inhibitors to translation remodelers that globally reprogram protein output and the translation machinery. As human patients begin treatment with these compounds, our discovery of rocaglate-inducible proteins and rocaglate-activated translation factors that drive drug-specific responses highlights an entirely uncharacterized yet critical aspect of rocaglate potency. These timely findings emphasize systemic translational modeling as a newer concept for cancer therapy, and advocate for a systematic overhaul in our understanding of drugs traditionally defined as translation inhibitors.

Citation Format: Jyun David Ho, Jr, Tyler A. Cunningham, Caroline A. Coughlin, Artavazd Arumov, Evan R. Roberts, Daniel Bilbao, Jonathan R. Krieger, Stephen Lee, Jonathan H. Schatz. Translatome and protein synthesis machinery remodeling by rocaglates drives antitumor activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1031.

Optimized Doxorubicin Chemotherapy for Diffuse Large B-cell Lymphoma Exploits Nanocarrier Delivery to Transferrin Receptors

New treatments are needed to address persistent unmet clinical needs for diffuse large B-cell lymphoma (DLBCL). Overexpression of transferrin receptor 1 (TFR1) is common across cancer and permits cell-surface targeting of specific therapies in preclinical and clinical studies of various solid tumors. Here, we developed novel nanocarrier delivery of chemotherapy via TFR1-mediated endocytosis, assessing this target for the first time in DLBCL. Analysis of published datasets showed novel association of increased TFR1 expression with high-risk DLBCL cases. Carbon-nitride dots (CND) are emerging nanoparticles with excellent in vivo stability and distribution and are adaptable to covalent conjugation with multiple substrates. In vitro, linking doxorubicin (Dox) and transferrin (TF) to CND (CND-Dox-TF, CDT) was 10-100 times more potent than Dox against DLBCL cell lines. Gain- and loss-of-function studies and fluorescent confocal microscopy confirmed dependence of these effects on TFR1-mediated endocytosis. In contrast with previous therapeutics directly linking Dox and TF, cytotoxicity of CDT resulted from nuclear entry by Dox, promoting double-stranded DNA breaks and apoptosis. CDT proved safe to administer in vivo, and when incorporated into standard frontline chemoimmunotherapy in place of Dox, it improved overall survival by controlling patient-derived xenograft tumors with greatly reduced host toxicities. Nanocarrier-mediated Dox delivery to cell-surface TFR1, therefore, warrants optimization as a potential new therapeutic option in DLBCL. SIGNIFICANCE: Targeted nanoparticle delivery of doxorubicin chemotherapy via the TRF1 receptor presents a new opportunity against high-risk DLBCL tumors using potency and precision.

Abstract PO-48: Cytotoxic mechanism of a novel transferrin receptor-targeting chemotherapeutic nanocarrier for use in diffuse large B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL), the most common hematologic malignancy, is an aggressive form of non-Hodgkin lymphoma. Approximately 60% of DLBCL patients achieve long-term disease-free survival from frontline R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisone), but patients with relapsed or refractory disease have poor prognosis. Doxorubicin (Dox) remains the most active anti-lymphoma agent, but its use is limited by well-characterized toxicities, including potentially irreversible cardiac damage. Targeted and specific delivery of Dox to tumors to overcome these limitations has been an area of active research. Targeted delivery of Dox via the transferrin receptor (TFR1) has preclinical efficacy in solid malignancies but has yet to be explored in lymphoma. We have uncovered for the first time a significant association between TFR1 expression and poor prognosis in DLBCL. Carbon-nitride dots (CNDs) are third-generation nanocarriers with inherent photoluminescence, which are easily conjugated with a wide variety of substrates. We conjugated Dox and transferrin (TF), the ligand for TFR1, to CNDs to develop CND-Dox-TF (CDT). CDT is uniquely designed to enhance Dox delivery to TFR1-expressing DLBCL tumors while limiting effects on nonmalignant tissues. BJAB and Farage cell lines treated with CDT for 24 hours underwent apoptosis at a significantly lower concentration when compared to Dox (50 nM vs. 1000 nM). Overall, CDT was 1-2 Log10 more potent than Dox against DLBCL cell lines. Co-incubation with 250 uM of antagonist holo-transferrin significantly decreased BJAB and Farage sensitivity to CDT, confirming activity through TFR1. Confocal microscopy of BJAB cells incubated up to 24 hours with 250 nM Dox and 30 nM CDT reveled enhanced nuclear colocalization of Dox at a significantly lower concentration. Prior dose-finding experiments in non-tumor bearing mice identified a CDT safe working dose of 33.0 mg/kg containing 16% moles of Dox in comparison to Dox maximum-tolerated dose (MTD) 3.3 mg/kg. We engrafted 2 groups of 10 NSG mice with a Dox-sensitive high-TFR1 expressing patient-derived xenograft (PDX) tumor. Mice were dosed with CDT and Dox on day 0, 14, and 24. CDT demonstrated similar anti-lymphoma efficacy with reduced toxicity: CDT-treated mice displayed no significant decline in body weight, which is characteristic and was observed following each single-agent Dox treatment. Histology analyses revealed little to no obvious damage to CDT-treated nonmalignant tissues, including myocardium. With a working dose of CDT identified, we now have under way clinically relevant R-CHOP vs. R-nanoCHOP (CDT substituted for Dox) assessments in our PDX mouse model. Capitalizing on the unique design, we expect to observe improved anti-lymphoma efficacy, with decreased toxicities and an improvement in overall survival. In sum, we provide mechanistic insight for novel DLBCL nano-chemotherapy and illustrate preclinical efficacy for a promising new therapeutic approach.

Citation Format: Artavazd Arumov, Piumi Y. Liyanage, Asaad Trabolsi, Evan R. Roberts, Braulio Ferreira, Daniel Bilbao, Roger M. LeBlanc, Jonathan H. Schatz. Cytotoxic mechanism of a novel transferrin receptor-targeting chemotherapeutic nanocarrier for use in diffuse large B-cell lymphoma [abstract]. In: Proceedings of the AACR Virtual Meeting: Advances in Malignant Lymphoma; 2020 Aug 17-19. Philadelphia (PA): AACR; Blood Cancer Discov 2020;1(3_Suppl):Abstract nr PO-48.

Phase II trial of bicalutamide in combination with palbociclib for the treatment of androgen receptor (+) metastatic breast cancer

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Background: Genome-wide transcriptional analysis has identified a unique subset of androgen receptor (AR) +, estrogen receptor (ER)/progesterone receptor (PR)- breast cancer (BC). The functional role of AR was confirmed initially in preclinical models demonstrating that androgen-driven growth could be abrogated by antiandrogen therapy. TBCRC011 established the safety and efficacy of inhibiting AR with bicalutamide (B) in patients (pts) with AR+/ER/PR- metastatic BC (MBC) with a median progression free survival (PFS) of 12 weeks (wks) (95% CI, 11–22 wks). In preclinical data, palbociclib (P) has been shown to reduce growth of AR+/ER/PR- MDA-MB-453 BC cells. It has been shown that AR+ triple negative BC (TNBC) expresses a luminal profile and has intact Rb protein, the target of P activity. We conducted this Phase I/II trial of the AR inhibitor B in combination with the CDK4/6 inhibitor P in pts with AR+/ER/PR/HER2- BC (NCT02605486) to test the hypothesis that androgen blockade, paired with CDK4/6 inhibition would have increased efficacy in pts with androgen-dependent BC. Methods: Postmenopausal pts with AR+ TN MBC defined as IHC ≥ 1% nuclear staining (DAKO, Clone AR441 (5/2016-11/2016) then Ventana AR SP107 (11/2016-6/2018), ECOG ≤2, measurable/non-measurable disease were eligible for enrollment. Any number of prior regimens was permitted. Pts received B 150 mg daily and P 125 mg daily 3 wks on 1 wk off. Pts were evaluated for toxicity every 2-4 wks and for response every 8-12 wks. Primary endpoint: 6 month (mo) PFS. Secondary endpoints: clinical benefit rate, toxicity, correlative studies to better characterize AR+ TNBC. A Simon 2-stage minimax design that discriminates between 6 mo PFS rates of 20% and 40% was used. If ≥ 11/33 pts were PF at 6 mo then B+P would warrant further study. Results: As of 1.1.20 33 pts were enrolled on study with median (med) age 67 (42-79), performance status 0 (0-1). Number of pts with visceral metastases: 20, measurable disease: 22. AR% 1-9: 3, 10-50: 6; 51-100: 24. Med prior lines for MBC: 3 (0-9). Best response: (31 evaluable pts): 11 pts PF at 6mo: 10 SD > 6mo, 1 PR. Med wks on study: 14 (2-101). Toxicity > 10% grade >3 related: Number of pts with leukopenia: 21, neutropenia: 21, lymphocytopenia: 6, thrombocytopenia: 3. One pt with febrile neutropenia. One death due to disease progression within 30 days off study. Conclusions: In this selected subset of pts with AR+ TN MBC, this study met its prespecified endpoint with 11 pts PF at 6 mo on B 150 mg + P 125 mg. B+P has been well tolerated with no unexpected toxicity observed. Clinical trial information: NCT02605486 .

Adjuvant enzalutamide for the treatment of early-stage androgen receptor-positive (AR+) TNBC

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Background: A subset of TNBC is dependent on AR signaling. Enzalutamide (ENZA), an AR-antagonist, has activity in patients (pts) with metastatic AR+ TNBC, with a clinical benefit rate of 33%. This study tests the feasibility of adjuvant ENZA for the treatment (tx) of early stage, AR+ TNBC. We now report the primary endpoint (endpt) and safety. Methods: Eligible pts have centrally confirmed, Stage I-III, ER/PR < 1%, HER2(-), AR ≥1% BC and completed all planned surgery, chemotx and radiation (RT) < 6 months of tx start. AR testing by IHC per MSK methods. Tx consists of ENZA 160mg daily for 1 year (y) with the option to extend tx to 2y. Toxicity per NCI CTCAEv4 every (q) 4 weeks (wk) for 12 wk, then q3 months. Primary endpt: feasibility of 1y ENZA defined as the discontinuation rate due to toxicity, consent withdrawal or tolerability. 50 pts are enrolled to have 46 evaluable pts required to discriminate between feasibility of 50% and 70%, with type I error 5% and 88% power. Pts who have disease progression (PD) or die during 1st y of ENZA and do not have tx discontinuation due to the above will not be included in the primary analysis. If 29 pts complete 1y, adjuvant ENZA will be deemed feasible. Secondary endpts: safety and 3y DFS and OS. Exploratory endpts: PROs and biomarker development. Results: Between 5/2016-6/2018, 50 pts were enrolled. Pt and tumor characteristics (N = 50): Median age 55y (33-81); Stage: I 20 (40%), II 23 (46%), III 7 (14%); Grade (gr): 2 = 26%, 3 = 74%. AR > 10% = 35 (70%), AR ≤10% = 15 (30%). Chemotx 47/50 (94%): Neoadjuvant (neo) 40%, Adjuvant (adj) 60%; Anthracycline/Taxane-based 38/47 (81%), Platinum 1/47 (2%), Docetaxel/Cyclophosphamide 3/47 (6%), other 5/47 (11%). 13/19 who received neo tx failed pCR; 9/13 (69.2%) received adj capecitabine. RT: 38/50 (76%). 27 pts completed 1y of tx. 7 pts will be evaluable by 6/1/19. 1 pt to complete 1y 6/21/19. 15 pts are off tx: PD (3), toxicity (5), noncompliance (4), withdrawal of consent (3). Tx-related AEs, any gr, > 10% (N = 50): fatigue (48%), hot flashes (22%), headache (18%), hyperglycemia (18%), nausea (18%), WBC decreased (16%), dizziness (14%), arthralgia (12%), dyspnea (12%). Tx-related, gr 3 AEs: fatigue (6%), hyperglycemia (2%), hypertension (2%). No gr 4/5 AEs or seizures. 11 pts had dose reduction. Conclusions: Feasibility of adjuvant ENZA will be fully evaluable in 4/2019 and is anticipated to meet the prespecified statistical expectations for primary endpt. ENZA is well tolerated following locoregional tx and standard of care systemic tx. Secondary analyses and correlatives are ongoing to define the role of AR in TNBC. Clinical trial information: NCT02750358.