Abstract 4720: Ataxia telangiectasia mutated (ATM) kinase inhibitor AZD0156 in combination with 5-fluorouracil and irinotecan in preclinical models of colorectal cancer

Background: AZD0156 is an oral inhibitor of ATM, a serine threonine kinase that plays a key role in DNA damage response associated with DNA double strand breaks. Topoisomerase-I inhibitors like irinotecan induce single-strand DNA breaks, which are converted to double-strand breaks during DNA replication. Thus the combination of AZD0156 and irinotecan is a rational combination for clinical use. Irinotecan is used clinically to treat a variety of malignancies, including colorectal cancer (CRC), usually in combination with 5-fluorouracil (5FU) as FOLFIRI. An ongoing phase 1 clinical trial is evaluating AZD0156 in combination with single-agent irinotecan and FOLFIRI in patients with refractory cancers (NCT02588105). The purpose of this study is to evaluate AZD0156 in combination with irinotecan and 5FU in preclinical models of CRC to help inform clinical use.

Methods: Anti-proliferative effects of single-agent AZD0156 and combination therapy with SN38 (active metabolite of irinotecan) and 5FU were evaluated in CRC cell lines using the Cell-Titer Glo assay. Immunoblotting and cell cycle analysis were performed to determine the mechanism of enhanced combination effects. Four CRC patient derived xenograft (PDX) models were treated with AZD0156, irinotecan, and 5FU alone and in combination for assessment of tumor growth inhibition (TGI).

Results: An enhanced antiproliferative effect was observed with the combination treatment over either single agent. A more significant synergistic effect was demonstrated with the combination of AZD0156 and SN38 as compared with the combination of AZD0156 and 5FU. Cell cycle data demonstrated enhanced cell cycle arrest with combination therapy as compared to single agents. Immunoblotting results suggest a decrease in phosphorylated gamma-H2AX in cell lines treated with combination therapies. Increased TGI was observed in CRC PDX models treated with the combination of AZD0156 and irinotecan as compared to single-agent therapy in 3 of 4 models. There was not a significant change in TGI with the addition of 5FU for triplet therapy in the majority of models.

Conclusions: The combination of AZD0156 with irinotecan is synergistic in in vitro models and is associated with increased TGI in CRC PDX in vivo models. The addition of 5FU to AZD0156 and irinotecan did not result in increased TGI as compared to doublet therapy in CRC PDX models, though did not decrease the AZD0156/irinotecan combination effect. An ongoing clinical trial is evaluating this combination in patients with cancers refractory to standard treatments (NCT02588105).

Citation Format: S. Lindsey Davis, Marina I. Schlaepfer, Stacey M. Bagby, Sarah J. Hartman, Betelehem W. Yacob, Tonia Tse, Dennis M. Simmons, Jennifer R. Diamond, Christopher H. Lieu, Alexis D. Leal, Elaine B. Cadogan, Gareth D. Hughes, Stephen T. Durant, Wells A. Messersmith, Todd M. Pitts. Ataxia telangiectasia mutated (ATM) kinase inhibitor AZD0156 in combination with 5-fluorouracil and irinotecan in preclinical models of colorectal cancer [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 4720.

Abstract 1315: Combination of Wee1 inhibition with targeted and standard chemotherapy in preclinical models of pancreatic ductal adenocarcinoma

Introduction: Pancreatic ductal adenocarcinoma (PDA) is the fourth leading cause of cancer death and has a 5-year survival rate of less than 7%. The poor prognosis associated with PDA is related in part to a lack of screening tests to promote early detection and ineffective systemic targeted therapies. Adavosertib (AZD1775, MK1775) is a selective Wee1 inhibitor with promising preclinical activity in PDA and synergy with cytotoxic chemotherapy in other cancer types. Wee1 is a tyrosine kinase that activates in the G2M cell cycle checkpoint in response to DNA damage. Inhibition of Wee1 with adavosertib prevents the phosphorylation of CDC2, thus allowing unrepaired DNA to enter mitosis and ultimately succumb to mitotic catastrophe. The purpose of this study was to investigate adavosertib in combination with standard chemotherapy and other targeted agents in preclinical models of PDA.

Methods: Athymic nude mice were implanted with PDA PDX models on the right and left flanks. When the average tumor volume reached 100-300 mm3, mice were randomized into one of the following treatments: vehicle, adavosertib, irinotecan, navitoclax, capecitabine, adavosertib + irinotecan, or adavosertib + navitoclax, adavosertib + capecitabine. Tumor volume was calculated using the following equation: volume = (length × width) × 0.52. Four pancreatic cancer cell lines were plated in 96-well plates and Cell Titer-Glo proliferation assays were performed to determine the most effective combination doses of irinotecan, 5FU, or navitoclax with adavosertib in vitro. Combination effects were analyzed using CalcuSyn software. The most effective doses within each cell line were selected and used for Caspase 3/7 apoptosis assays and cell cycle analyses by flow cytometry. Western blots were performed to evaluate changes in downstream effectors.

Results: In vivo, the combination of adavosertib with either irinotecan or navitoclax resulted in decreased tumor growth compared to the respective single agents. The combination of adavosertib with irinotecan, 5FU, or navitoclax in vitro resulted in greater antiproliferative effects in all cell lines, and the several combinations were synergistic in all cell lines as determined by CI values less than 1. Navitoclax increased apoptosis in several cell lines both as a single agent and was enhanced in combination with adavosertib. Irinotecan proved to be more cell cycle dependent and significantly altered the cell cycle in all cell lines. Irinotecan increased phospho-CDC2 and decreased PHH3, while adavosertib increased gamma-H2AX as a single agent and in combination.

Conclusions: The combination of adavosertib with either irinotecan, 5FU, or navitoclax in vivo decreased tumor growth and had enhanced antiproliferative effects in vitro. These data support future studies with adavosertib in combination with standard therapies or navitoclax to treat PDA.

Citation Format: Sarah J. Hartman, Stacey M. Bagby, Betelehem W. Yacob, Dennis M. Simmons, Tonia E. Tse, Christopher H. Lieu, S. Lindsey Davis, Alexis D. Leal, Jennifer R. Diamond, Wells A. Messersmith, Todd M. Pitts. Combination of Wee1 inhibition with targeted and standard chemotherapy in preclinical models of pancreatic ductal adenocarcinoma [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 1315.

Combination of Trastuzumab Emtansine and Stereotactic Radiosurgery Results in High Rates of Clinically Significant Radionecrosis and Dysregulation of Aquaporin-4

PURPOSE

Patients with human EGFR2-positive (HER2⁺) breast cancer have a high incidence of brain metastases, and trastuzumab emtansine (T-DM1) is often employed. Stereotactic radiosurgery (SRS) is frequently utilized, and case series report increased toxicity with combination SRS and T-DM1. We provide an update of our experience of T-DM1 and SRS evaluating risk of clinically significant radionecrosis (CSRN) and propose a mechanism for this toxicity.

EXPERIMENTAL DESIGN

Patients with breast cancer who were ≤45 years regardless of HER2 status or had HER2⁺ disease regardless of age and underwent SRS for brain metastases were included. Rates of CSRN, SRS data, and details of T-DM1 administration were recorded. Proliferation and astrocytic swelling studies were performed to elucidate mechanisms of toxicity.

RESULTS

A total of 45 patients were identified; 66.7% were HER2⁺, and 60.0% were ≤ 45 years old. Of the entire cohort, 10 patients (22.2%) developed CSRN, 9 of whom received T-DM1. CSRN was observed in 39.1% of patients who received T-DM1 versus 4.5% of patients who did not. Receipt of T-DM1 was associated with a 13.5-fold (P = 0.02) increase in CSRN. Mechanistically, T-DM1 targeted reactive astrocytes and increased radiation-induced cytotoxicity and astrocytic swelling via upregulation of Aquaporin-4 (Aqp4).

CONCLUSIONS

The strong correlation between development of CSRN after SRS and T-DM1 warrants prospective studies controlling for variations in timing of T-DM1 and radiation dosing to further stratify risk of CSRN and mitigate toxicity. Until such studies are completed, we advise caution in the combination of SRS and T-DM1.

Atezolizumab Plus nab-Paclitaxel in the Treatment of Metastatic Triple-Negative Breast Cancer With 2-Year Survival Follow-up: A Phase 1b Clinical Trial

Importance

The humanized monoclonal antibody atezolizumab targets programmed death-ligand 1 and has demonstrated durable single-agent activity in a subset of metastatic triple-negative breast cancers. To extend the observed activity, combinatorial approaches are being tested with standard cytotoxic chemotherapies known to induce immunogenic tumor cell death.

Objective

To examine the safety, tolerability, and preliminary clinical activity of atezolizumab plus nab-paclitaxel in metastatic triple-negative breast cancers.

Design, Setting, and Participants

This phase 1b multicohort study enrolled 33 women with stage IV or locally recurrent triple-negative breast cancers and 0 to 2 lines of prior chemotherapy in the metastatic setting from December 8, 2014, to April 30, 2017, at 11 sites in the United States. The median follow-up was 24.4 months (95% CI, 22.1-28.8 months).

Interventions

Patients received concurrent intravenous atezolizumab and intravenous nab-paclitaxel (minimum 4 cycles).

Main Outcomes and Measures

The primary end point was safety and tolerability. Secondary end points included best overall response rate by Response Evaluation Criteria in Solid Tumors, version 1.1; objective response rate; duration of response; disease control rate; progression-free survival; overall survival; and biomarker analyses.

Results

The 33 women had a median age of 55 years (range, 32-84 years) and received 1 or more doses of atezolizumab. All patients (100%) experienced at least 1 treatment-related adverse event, 24 patients (73%) experienced grade 3/4 adverse events, and 7 patients (21%) had grade 3/4 adverse events of special interest. No deaths were related to study treatment. The objective response rate was 39.4% (95% CI, 22.9%-57.9%), and the median duration of response was 9.1 months (95% CI, 2.0-20.9 months). The disease control rate was 51.5% (95% CI, 33.5%-69.2%). Median progression-free survival and overall survival were 5.5 months (95% CI, 5.1-7.7 months) and 14.7 months (95% CI, 10.1-not estimable), respectively. Concurrent nab-paclitaxel neither significantly changed biomarkers of the tumor immune microenvironment (programmed death-ligand 1, tumor-infiltrating lymphocytes, CD8) nor impaired atezolizumab systemic immune activation (expansion of proliferating CD8+ T cells, increase of CXCL10 chemokine).

Conclusions and Relevance

In this phase 1b trial for metastatic triple-negative breast cancers, the combination of atezolizumab plus nab-paclitaxel had a manageable safety profile. Antitumor responses were observed, including in patients previously treated with a taxane.

Trial Registration

ClinicalTrials.gov identifier: NCT01633970.

Sacituzumab Govitecan-hziy in Refractory Metastatic Triple-Negative Breast Cancer

BACKGROUND

Standard chemotherapy is associated with low response rates and short progression-free survival among patients with pretreated metastatic triple-negative breast cancer. Sacituzumab govitecan-hziy is an antibody-drug conjugate that combines a humanized monoclonal antibody, which targets the human trophoblast cell-surface antigen 2 (Trop-2), with SN-38, which is conjugated to the antibody by a cleavable linker. Sacituzumab govitecan-hziy enables delivery of high concentrations of SN-38 to tumors.

METHODS

We conducted a phase 1/2 single-group, multicenter trial involving patients with advanced epithelial cancers who received sacituzumab govitecan-hziy intravenously on days 1 and 8 of each 21-day cycle until disease progression or unacceptable toxic effects. A total of 108 patients received sacituzumab govitecan-hziy at a dose of 10 mg per kilogram of body weight after receiving at least two previous anticancer therapies for metastatic triple-negative breast cancer. The end points included safety; the objective response rate (according to Response Evaluation Criteria in Solid Tumors, version 1.1), which was assessed locally; the duration of response; the clinical benefit rate (defined as a complete or partial response or stable disease for at least 6 months); progression-free survival; and overall survival. Post hoc analyses determined the response rate and duration, which were assessed by blinded independent central review.

RESULTS

The 108 patients with triple-negative breast cancer had received a median of 3 previous therapies (range, 2 to 10). Four deaths occurred during treatment; 3 patients (2.8%) discontinued treatment because of adverse events. Grade 3 or 4 adverse events (in ≥10% of the patients) included anemia and neutropenia; 10 patients (9.3%) had febrile neutropenia. The response rate (3 complete and 33 partial responses) was 33.3% (95% confidence interval [CI], 24.6 to 43.1), and the median duration of response was 7.7 months (95% CI, 4.9 to 10.8); as assessed by independent central review, these values were 34.3% and 9.1 months, respectively. The clinical benefit rate was 45.4%. Median progression-free survival was 5.5 months (95% CI, 4.1 to 6.3), and overall survival was 13.0 months (95% CI, 11.2 to 13.7).

CONCLUSIONS

Sacituzumab govitecan-hziy was associated with durable objective responses in patients with heavily pretreated metastatic triple-negative breast cancer. Myelotoxic effects were the main adverse reactions. (Funded by Immunomedics; IMMU-132-01 ClinicalTrials.gov number, NCT01631552.).

Abstract P2-11-01: Safety and efficacy of sacituzumab govitecan (anti-Trop-2-SN-38 antibody-drug conjugate) as ≥3rd-line therapeutic option for treatment-refractory HER2-negative metastatic breast cancer (HER2Neg mBC)

Background: Sacituzumab govitecan is an antibody-drug conjugate consisting of SN-38, the active metabolite of irinotecan, conjugated to a humanized mAb targeting Trop-2 (trophoblastic antigen-2), which is highly expressed in many epithelial cancers. A phase I/II basket trial (NCT01631552) investigated its activity in patients (pts) with advanced epithelial cancers. Herein, we summarize pooled safety and efficacy findings in 162 pts with HER2-negative metastatic breast cancer (mBC) accrued between 7/2013 and 6/2017 who received at least 2 prior therapies for metastatic disease and were treated with sacituzumab govitecan at the 10 mg/kg dose level.

Methods: Patients with triple-negative (N=108) and patients with hormone-receptor positive (N=54) mBC received 10 mg/kg sacituzumab govitecan on days 1 & 8 of a 21-day cycle continued until progression or unacceptable toxicity. All pts had measurable disease by CT or MRI. Efficacy was assessed locally by RECIST 1.1 including overall response rate (ORR) and Kaplan-Meier estimates of duration of response (DOR), progression-free survival (PFS) and overall survival (OS). Adverse events (AE) were evaluated according to CTCAE v4.0

Results: The patient cohort (161 female /1 male; median age 55 yrs, range 31-80) received a median of 4 prior therapies for metastatic disease (range 2-17), with prior chemotherapy agents in the metastatic setting including taxane (68%), capecitabine (60%), platinum (59%), gemcitabine (44%), eribulin (41%), and anthracycline (38%). 77 pts have died, with 57 in long-term follow-up and 28 still on treatment at data cutoff. The median number of administered sacituzumab govitecan doses was 14 (range 1-88). Treatment was generally well tolerated. 29% of pts had dose reductions, 3% discontinued treatment due to drug-related AEs, and there were no treatment-related deaths. Based on currently available AE data, grade ≥ 3 toxicity included neutropenia (43%), anemia (9.5%), diarrhea (7.0%) and febrile neutropenia (6.3%). For the TNBC subgroup, with a median follow-up of 9.3 months, the ORR was 33% (3 CRs + 33 PRs /108) with a median DOR of 8.3 months (95% CI: 4.8 – 11.6). For the ER+ subgroup, with a median follow-up of 10.0 months, the ORR was 31% (17 PRs/54) with a median DOR of 7.4 months (95% CI: 4.4 – 18.3). The combined HER2Neg ORR was 33% (3 CRs+50 PRs/162), with a median DOR of 8.3 months (95% CI: 4.9 - 10.8), PFS of 5.6 months (95% CI: 5.1 – 6.9) and OS of 13.0 months (95% CI: 11.5 - 15.0). The ORR was comparable for pts ≤ 50 yrs. old [32.2% (19/59)] vs. > 50 yrs old [33.0% (34/103)] and little different for pts with 2 prior therapies [35.4% (17/48)] vs. >2 prior therapies [31.6% (36/114)].

Conclusions: Monotherapy with sacituzumab govitecan was well tolerated with a manageable safety profile, and achieved a 30+% objective response rate among heavily pre-treated patients with HER2-negative metastatic breast cancer regardless of ER status.

Citation Format: Kalinsky K, Isakoff SJ, Tolaney SM, Juric D, Mayer IA, Vahdat LT, Diamond JR, O'Shaughnessy J, Moroose RL, Santin AD, Shah NC, Abramson V, Goldenberg DM, Sharkey RM, Washkowitz SA, Wegener WA, Iannone R, Bardia A. Safety and efficacy of sacituzumab govitecan (anti-Trop-2-SN-38 antibody-drug conjugate) as ≥3rd-line therapeutic option for treatment-refractory HER2-negative metastatic breast cancer (HER2Neg mBC) [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-11-01.

Abstract P2-06-15: Rational combination of Wee1 and BCL-2 inhibition in preclinical models of triple-negative breast cancer

Background:

Triple-negative breast cancer (TNBC) is an aggressive subtype distinguished by its lack of expression of receptors for estrogen, progesterone, and normal human epidermal growth factor 2 expression. TNBC is difficult to treat and is associated with a high risk of recurrence and mortality. In order to effectively treat TNBC, alternative therapeutic targets need to be identified. Wee1 is a tyrosine kinase that phosphorylates CDC2 to pause the cell cycle at the G2 checkpoint as a means to delay mitosis while DNA damage undergoes repair. Inactivation of Wee1 via adavosertib (AZD1775, MK1775), a highly selective inhibitor of Wee1, allows CDC25 to dephosphorylate the CDC2/cyclin B complex resulting in premature initiation of mitosis and, ultimately, mitotic catastrophe and apoptosis. An unbiased screen of adovosertib in combination with other targeted compounds in TNBC patient-derived xenograft (PDX) models demonstrated that the combination of adavosertib and navitoclax, an inhibitor of anti-apoptotic BCL-2 and BCL-XL proteins, had greater efficacy than the single agents alone. The purpose of this study was to investigate the combination of adavosertib and navitoclax in preclinical TNBC models, both in vitro and in vivo.

Methods:

HCC1937, CAL51, MDA-MB-231 and MDA-MB-468 cells were plated in 96-well plates and exposed to increasing concentrations of adavosertib (125nM – 1000nM), navitoclax (2500nM – 10000nM), or the combination. Cellular proliferation was assessed in real-time using IncuCyte Live Cell Analysis, followed by endpoint sulforhodamine B (SRB) assay. Combination effects were analyzed using Calcusyn to determine combination indexes (CI). Apoptosis was assessed via the Caspase 3/7 assay. Western blotting was used to assess changes in expression of CDC2, phospho-CDC2, and BCL2. TNBC PDX models CU_TNBC_013 and CU_TNBC_014 were treated with vehicle, adavosertib (50mg/kg), navitoclax (100mg/kg), or the combination and assessed for tumor growth inhibition.

Results:

The combination of adavosertib and navitoclax resulted in greater antiproliferative effects in vitro compared to either single agent (p< 0.05). This effect was classified as synergistic with CI values <1. We observed a significant increase in apoptosis with the combination treatment as measured by Caspase 3/7 (p <0.005). The combination of adavosertib and navitoclax treatment resulted in a decrease in phospo-CDC2, and BCL2 in cell lines. In vivo, the combination treatment resulted in greater tumor growth inhibition as compared to adavosertib or navitoclax alone in the CU_TNBC_013 and CU_TNBC_014 PDX models.

Conclusions:

The combination of adavosertib and navitoclax is active in preclinical TNBC models and induces apoptosis and tumor growth inhibition. This data supports the continued development of this combination in TNBC with investigation of potential selective markers.

Citation Format: Simmons DM, Tse TE, Dailey K, Hartman SJ, Bagsby S, Pitts TM, Tentler JJ, Diamond JR. Rational combination of Wee1 and BCL-2 inhibition in preclinical models of triple-negative breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-06-15.

Abstract PD1-09: Phase 2 safety and efficacy results of TAK-228 in combination with exemestane or fulvestrant in postmenopausal women with ER-positive/HER2-negative metastatic breast cancer previously treated with everolimus

Background: TAK-228 is an investigational, oral and highly selective ATP-competitive inhibitor of TORC1/2. Targeting the PI3K/AKT/mTOR pathway with the dual TORC1/2 inhibitor TAK-228 may restore sensitivity to endocrine therapies in patients (pts) with breast cancer who have progressed on the combination of an endocrine agent plus a TORC1 inhibitor. Here we report data from the phase 2 portion of a phase 1b/2 study of TAK-228 plus exemestane (E) or fulvestrant (F).

Methods: Postmenopausal women with ER+ and HER2-, inoperable or metastatic breast cancer (MBC) following everolimus (EVE) plus E or F after progression, received oral TAK-228 (4 mg QD) plus E (25 mg QD) or F (500 mg monthly) for 28-day cycles until progressive disease (PD) or unacceptable toxicity (NCT02049957). Pts were enrolled into parallel cohorts based on prior response to EVE plus E or F and were given the same prior therapy (E or F) at their established dose: EVE-sensitive, defined as disease progression after complete response (CR), partial response (PR), or ≥6 mos stable disease (SD); or EVE-resistant, defined as disease progression without a CR or PR, or after <6 mos SD. Primary endpoint was clinical benefit rate at 16 wks (CR, PR, or SD at 16 wks; CBR-16). Secondary endpoints included CBR at 24 wks (CBR-24), overall response rate (ORR), progression-free survival (PFS), overall survival (OS) and safety.

Results: From Oct 2015 to Dec 2017, 94 pts were enrolled. Median age was 58 y (range 32–83). At baseline, most pts (67%) had stage IV disease and others were stage IA–IIIC (24%), other (3%) or unknown (5%); 94% of EVE-sensitive (93% E vs 100% F) and 88% of EVE-resistant pts (91% E vs 75% F) had received ≥4 prior lines of therapy. Pts received a median of 3 cycles (1–15) of TAK-228. At data cutoff (24 Apr 2018), 98% of pts had discontinued treatment, mainly due to PD (76%) or adverse events (AEs; 14%). CBR-16 was 41% (n=21) in EVE-sensitive and 26% (n=11) in EVE-resistant pts (table). CBR-24 was 24% in EVE-sensitive (19% E vs 50% F) and 23% in EVE-resistant (23% E vs 25% F) pts. Eleven of 21 pts who achieved CBR-16 also achieved CBR-24 (6 SD, 5 PR) in the EVE-sensitive cohort and 8 of 11 pts in the EVE-resistant cohort (6 SD, 2 PR). The ORR was 12% in EVE-sensitive pts and 9% in EVE-resistant pts (table). Median PFS (95% CI) was 4.1 mos (2.2–5.5) and 3.4 mos (1.9–5.4), and median OS (95% CI) was 15.9 mos (14.1–19.5) and 14.0 mos (13.0–16.0) in the EVE-sensitive and -resistant cohorts, respectively. Drug-related any grade and grade ≥3 AEs were seen in 90% and 29% of pts, respectively. Most common drug-related any grade AEs were nausea (50%), fatigue (38%), hyperglycemia and diarrhea (each 29%); 22% of pts reported a serious AE. No deaths were reported. Treatment is ongoing in two pts.

Conclusion: TAK-228 plus E or F showed modest clinical benefit in pts with previously treated, EVE-sensitive or -resistant MBC, with an acceptable safety profile.

 EVE-sensitive (N=51)EVE-resistant (N=43) TAK-228+TAK-228+Best response, n (%)E (n=43)F (n=8)E (n=35)F (n=8)ORR=CR+PR4 (9)2 (25)3 (9)1 (13)CR001 (3)0PR4 (9)2 (25)2 (6)1 (13)CBR-1617 (40)4 (50)9 (26)2 (25)

Citation Format: Diamond JR, Potter D, Salkeni M, Silverman P, Haddad T, Forget F, Awada A, Canon J-L, Danso M, Lortholary A, Bourgeois H, Tan-Chiu E, Patel C, Neuwirth R, Leonard EJ, Lim B. Phase 2 safety and efficacy results of TAK-228 in combination with exemestane or fulvestrant in postmenopausal women with ER-positive/HER2-negative metastatic breast cancer previously treated with everolimus [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD1-09.

Characterization of immune responses to anti-PD-1 mono and combination immunotherapy in hematopoietic humanized mice implanted with tumor xenografts

Background

The success of agents that reverse T-cell inhibitory signals, such as anti-PD-1/PD-L1 therapies, has reinvigorated cancer immunotherapy research. However, since only a minority of patients respond to single-agent therapies, methods to test the potential anti-tumor activity of rational combination therapies are still needed. Conventional murine xenograft models have been hampered by their immune-compromised status; thus, we developed a hematopoietic humanized mouse model, hu-CB-BRGS, and used it to study anti-tumor human immune responses to triple-negative breast cancer (TNBC) cell line and patient-derived colorectal cancer (CRC) xenografts (PDX).

Methods

BALB/c-Rag2^nullIl2rγ^nullSIRPα^NOD (BRGS) pups were humanized through transplantation of cord blood (CB)-derived CD34+ cells. Mice were evaluated for human chimerism in the blood and assigned into experimental untreated or nivolumab groups based on chimerism. TNBC cell lines or tumor tissue from established CRC PDX models were implanted into both flanks of humanized mice and treatments ensued once tumors reached a volume of ~150mm³. Tumors were measured twice weekly. At end of study, immune organs and tumors were collected for immunological assessment.

Results

Humanized PDX models were successfully established with a high frequency of tumor engraftment. Humanized mice treated with anti-PD-1 exhibited increased anti-tumor human T-cell responses coupled with decreased Treg and myeloid populations that correlated with tumor growth inhibition. Combination therapies with anti-PD-1 treatment in TNBC-bearing mice reduced tumor growth in multi-drug cohorts. Finally, as observed in human colorectal patients, anti-PD-1 therapy had a strong response to a microsatellite-high CRC PDX that correlated with a higher number of human CD8+ IFNγ+ T cells in the tumor.

Conclusion

Hu-CB-BRGS mice represent an in vivo model to study immune checkpoint blockade to human tumors. The human immune system in the mice is inherently suppressed, similar to a tumor microenvironment, and thus allows growth of human tumors. However, the suppression can be released by anti-PD-1 therapies and inhibit tumor growth of some tumors. The model offers ample access to lymph and tumor cells for in-depth immunological analysis. The tumor growth inhibition correlates with increased CD8 IFNγ+ tumor infiltrating T cells. These hu-CB-BRGS mice provide a relevant preclinical animal model to facilitate prioritization of hypothesis-driven combination immunotherapies.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0518-z) contains supplementary material, which is available to authorized users.

A first-in-human phase 1a study of the bispecific anti-DLL4/anti-VEGF antibody navicixizumab (OMP-305B83) in patients with previously treated solid tumors

Purpose Navicixizumab (OMP-305B83) is a bispecific antibody that inhibits delta-like ligand 4 and vascular endothelial growth factor. This Phase 1a trial assessed escalating doses of navicixizumab in refractory solid tumors patients. Design A 3 + 3 dose escalation design was used followed by the treatment of additional patients in an expansion cohort. Study objectives were determination of the maximum tolerated dose, safety, pharmacokinetics, pharmacodynamics, immunogenicity and efficacy. Results Sixty-six patients were treated once every 3 weeks in 8 dose-escalation cohorts (0.5, 1, 2.5, 3.5, 5, 7.5, 10, and 12.5 mg/kg) and an expansion cohort (7.5 mg/kg). The median age was 60 years and 68% of the patients were female. The most commonly enrolled tumor types were ovarian (12), colorectal (11) and breast, pancreatic, uterine and endometrial (4 each) cancers. As only 1 dose limiting toxicity occurred, the maximum tolerated dose was not reached, but 7.5 mg/kg was chosen as the dose for the expansion cohort. The treatment related adverse events (≥15% of patients) were hypertension (57.6%), headache (28.8%), fatigue (25.8%), and pulmonary hypertension (18.2%). Pulmonary hypertension was mostly asymptomatic at doses ≤5 mg/kg (6 Gr1, 1 Gr2), but was more severe at higher doses (4 Gr2, 1 Gr3). Navicixizumab's half-life was 11.4 days and there was a moderate (29%) incidence of anti-drug antibody formation. Four patients (3 ovarian cancer, 1 uterine carcinosarcoma) had a partial response and 17 patients had stable disease. Nineteen patients had a reduction in the size of their target lesions including 7/11 patients with ovarian cancer. Four patients remained on study for >300 days and 2 of these patients were on study for >500 days. Conclusions Navicixizumab can be safely administered with manageable toxicities and these data showed preliminary signs of antitumor activity in multiple tumor types, but was most promising in ovarian cancer. As a result these data justify its continued development in combination Phase 1b clinical trials.

A Phase I Dose-Escalation Study of Linsitinib (OSI-906), a Small-Molecule Dual Insulin-Like Growth Factor-1 Receptor/Insulin Receptor Kinase Inhibitor, in Combination with Irinotecan in Patients with Advanced Cancer

Lessons Learned.

The maximum tolerated dose of the combination of linsitinib and irinotecan is linsitinib 450 mg daily on days 1–3 every 7 days and irinotecan 125 mg/m² days 1 and 8 of a 21‐day cycle.

The adverse effects associated with the combination are not significantly increased beyond what is expected of each drug as a single agent.

Multiple negative trials of insulin‐like growth factor‐1 receptor inhibitors performed in unselected patient populations led to the early discontinuation of linistinib development and this trial.

Earlier integration of assessment of potential predictive biomarkers into clinical trials, as was planned in this study, is vital to the development of targeted therapies in oncology.

Background.

This phase I dose‐escalation study was designed to evaluate the safety and tolerability of the combination of irinotecan and insulin‐like growth factor‐1 receptor (IGF‐1R) inhibitor linsitinib in patients with advanced cancer refractory to standard therapy.

Methods.

Dose escalation in three specified dose levels was performed according to a standard 3 + 3 design. Dose levels were as follows: (a) linsitinib 400 mg and irinotecan 100 mg/m², (b) linsitinib 450 mg and irinotecan 100 mg/m², and (c) linsitinib 450 mg and irinotecan 125 mg/m². Linisitinib was administered once daily on days 1–3, 8–10, and 15–17, and irinotecan on days 1 and 8. Assessment of a candidate predictive biomarker was planned in all patients, with further evaluation in an expansion cohort of advanced colorectal cancer.

Results.

A total of 17 patients were treated, with 1 patient in both cohort 2 and 3 experiencing dose‐limiting toxicity. Linsitinib 450 mg and irinotecan 125 mg/m² was the maximum tolerated dose. Sixteen (94%) patients experienced at least one treatment‐related adverse event. Neutropenia was the only grade >3 toxicity (4%). No significant hyperglycemia or QT interval prolongation was noted. No objective responses were observed; 47% (n = 8) had stable disease with median duration of 5.25 months.

Conclusion.

Although the combination was determined safe, the study was halted due to termination of linsitinib development, and biomarker testing was not performed.

A phase II clinical trial of the Aurora and angiogenic kinase inhibitor ENMD-2076 for previously treated, advanced, or metastatic triple-negative breast cancer

Background

Triple-negative breast cancer (TNBC) remains an aggressive breast cancer subtype with limited treatment options. ENMD-2076 is a small-molecule inhibitor of Aurora and angiogenic kinases with proapoptotic and antiproliferative activity in preclinical models of TNBC.

Methods

This dual-institution, single-arm, two-stage, phase II clinical trial enrolled patients with locally advanced or metastatic TNBC previously treated with one to three prior lines of chemotherapy in the advanced setting. Patients were treated with ENMD-2076 250 mg orally once daily with continuous dosing in 4-week cycles until disease progression or unacceptable toxicity occurred. The primary endpoint was 6-month clinical benefit rate (CBR), and secondary endpoints included progression-free survival, pharmacokinetic profile, safety, and biologic correlates in archival and fresh serial tumor biopsies in a subset of patients.

Results

Forty-one patients were enrolled. The 6-month CBR was 16.7% (95% CI, 6–32.8%) and included two partial responses. The 4-month CBR was 27.8% (95% CI, 14–45.2%), and the average duration of benefit was 6.5 cycles. Common adverse events included hypertension, fatigue, diarrhea, and nausea. Treatment with ENMD-2076 resulted in a decrease in cellular proliferation and microvessel density and an increase in p53 and p73 expression, consistent with preclinical observations.

Conclusions

Single-agent ENMD-2076 treatment resulted in partial response or clinical benefit lasting more than 6 months in 16.7% of patients with pretreated, advanced, or metastatic TNBC. These results support the development of predictive biomarkers using archival and fresh tumor tissue, as well as consideration of mechanism-based combination strategies.

Trial registration

ClinicalTrials.gov, NCT01639248. Registered on July 12, 2012.

Abstract CT028: Atezolizumab (atezo) + nab-paclitaxel (nab-pac) in metastatic triple-negative breast cancer (mTNBC): 2-year update from a ph Ib trial

Introduction: Outcomes for patients (pts) with mTNBC remain poor, with chemotherapy as a historic mainstay treatment. Atezo (anti-PD-L1) demonstrated single-agent activity in mTNBC, and initial data suggested the addition of chemotherapy was safe with encouraging activity (Adams, 2016). Here we report long-term outcomes, with OS, for atezo + nab-pac in mTNBC.

Methods: Arm F of multi-cohort Ph Ib study (NCT01633970) enrolled pts with locally advanced unresectable/stage IV mTNBC and 0 to 2 prior regimens for advanced disease. Atezo 800 mg IV q2w and nab-pac 125 mg/m2 IV qw (3 weeks on/1 week off) were given concurrently (with nab-pac run-in for biopsy cohort); maintenance atezo was permitted until loss of clinical benefit. In-tumor PD-L1 expression (VENTANA SP142 assay), CD8 and stromal TILs were assessed by IHC; blood-based CD8+Ki67+ via FACS, and CXCL10 cytokine RNA by NanoString.

Results: Of 33 evaluable pts, 82% had ECOG PS 1, 58% had visceral mets, and median age was 55 years (data cutoff, April 30, 2017). Grade 3-4 treatment-related AEs (TRAE) occurred in 73%, with no Grade 5 TRAEs. Atezo-related AEs ≥ 20% included fatigue, pyrexia and decreased neutrophil count. Five pts discontinued nab-pac due to typical chemotherapy-related toxicities, and 3 withdrew from atezo due to TRAEs. Responses occurred across all subgroups (Table), with numerically higher ORR and longer OS/PFS in pts with less pre-treatment and higher PD-L1 status. Serial biopsy samples (n = 14) had elevated PD-L1+ TILs after combination treatment (but not after nab-pac alone). Peripheral blood analyses found transient on-treatment increases in CD8+Ki67+ and CXCL10, which were independent of efficacy.

Conclusions: In this single-arm study cohort, atezo + nab-pac was well tolerated with promising efficacy, especially for treatment-naive pts. Ongoing randomized Ph III trial IMpassion130 (NCT02425891) is investigating this regimen in untreated mTNBC.

Table. EfficacySubgroup/OutcomeCurrent Line of TherapyPD-L1 IC StatusaAll Ptsb (N = 33)1L (n = 13)2L+c (n = 20)IC1/2/3  (n = 12)IC0 (n = 12)Confirmed ORR (95% CI)54% (25, 81)30% (12, 54)42% (15, 72)33% (10, 65)39% (23, 58)mDOR (range)7.8 mo (2.9-11.5+)10.9 mo (3.7-20.9+)9.1 mo (2.9-16.2)10.2 mo (3.7-20.9+)9.1 mo (2.9-20.9+)mPFS (95% CI)8.6 mo (5.2, 11.5)5.1 mo (3.3, 7.3)6.9 mo (5.2, 11.0)5.1 mo (3.5, 6.8)5.5 mo (5.1, 7.7)mOS (95% CI)24.2 mo (11.5, NE)12.4 mo (7.5, 21.9)21.9 mo (13.1, NE)11.4 mo (7.5, NE)14.7 mo (10.1, NE)IC, tumor-infiltrating immune cells; mDOR, median duration of response; mPFS, median progression-free survival; mOS, median overall survival; mTNBC, metastatic triple-negative breast cancer; NE, not estimable; ORR, objective response rate; PD-L1, programmed death-ligand 1.a Excludes 9 pts with unknown PD-L1 status.b Includes 25 pts enrolled in the serial biopsy cohort and 8 in the safety cohort. Median durations of atezolizumab exposure, safety follow-up and efficacy follow-up were 5.6 mo (range, 0-30), 6.9 mo (range, 1.7-30.3) and 24.4 mo (95% CI: 22.1, 28.8), respectively.cIncludes 1 pt who received 3 prior therapies for mTNBC.Citation Format: Paula R. Pohlmann, Jennifer R. Diamond, Erika Hamilton, Sara M. Tolaney, Wei Zhang, Koho Iizuka, Paul Foster, Luciana Molinero, Roel Funke, Sylvia Adams. Atezolizumab (atezo) + nab-paclitaxel (nab-pac) in metastatic triple-negative breast cancer (mTNBC): 2-year update from a ph Ib trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr CT028.

Antitumor activity of the aurora a selective kinase inhibitor, alisertib, against preclinical models of colorectal cancer

Background

The Aurora kinases are a family of serine/threonine kinases comprised of Aurora A, B, and C which execute critical steps in mitotic and meiotic progression. Alisertib (MLN8237) is an investigational Aurora A selective inhibitor that has demonstrated activity against a wide variety of tumor types in vitro and in vivo, including CRC.

Results

CRC cell lines demonstrated varying sensitivity to alisertib with IC₅₀ values ranging from 0.06 to > 5 umol/L. Following exposure to alisertib we observed a decrease in pAurora A, B and C in four CRC cell lines. We also observed an increase in p53 and p21 in a sensitive p53 wildtype cell line in contrast to the p53 mutant cell line or the resistant cell lines. The addition of alisertib to standard CRC treatments demonstrated improvement over single agent arms; however, the benefit was largely less than additive, but not antagonistic.

Methods

Forty-seven CRC cell lines were exposed to alisertib and IC₅₀s were calculated. Twenty-one PDX models were treated with alisertib and the Tumor Growth Inhibition Index was assessed. Additionally, 5 KRAS wildtype and mutant PDX models were treated with alisertib as single agent or in combination with cetuximab or irinotecan, respectively.

Conclusion

Alisertib demonstrated anti-proliferative effects against CRC cell lines and PDX models. Our data suggest that the addition of alisertib to standard therapies in colorectal cancer if pursued clinically, will require further investigation of patient selection strategies and these combinations may facilitate future clinical studies.

Abstract P5-21-16: Preclinical studies of RX-5902, a beta-catenin modulator in triple negative breast cancer

Background: RX-5902 (Supinoxin) is a novel anti-cancer compound that targets phosphorylated p68 RNA helicase, a member of the DEAD box family of helicases, affecting upstream and downstream molecules in the Wnt canonical pathway. As a single agent, RX-5902 exhibits strong growth inhibition in both in vitro and in vivo settings. Specifically, RX-5902 enhances survival and tumor growth inhibition in numerous xenograft models, including ovarian, renal and breast. We have previously shown RX-5902 inhibits cell growth in a dose-dependent fashion in the triple-negative breast cancer (TNBC) xenograft MDA-MB231. In the current study, we have expanded our investigation of the therapeutic potential of RX-5902 against TNBC using both in vitro and in vivo preclinical models.

Methods: RX-5902 was provided by Rexahn, Inc. (Rockville, MD). Cell proliferation was measured using the Cell-Titer Glo luminescent cell viability assay (Promega). Apoptosis was assessed using Incucyte Caspase 3/7 Green apoptosis assay (Essenbioscience). Immunoblots of MDA-MB-231 cell line were probed for ß-catenin (Cell Signaling). Syngeneic 4T1 murine TNBC mice were obtained from Sippr-BK Laboratory Animal Co (Shanghai, China) and tumor volumes were measured twice a week. When the mean tumor volumes reached ˜90 mm3, mice were randomized and treated with vehicle or RX-5902 PO daily alone or in combination with anti-CTLA4 or anti-PD-1 BIW for 3 weeks. Tumor growth inhibition (TGI) was calculated at Day 25.

Results: A panel of 18 TNBC cell lines were treated with RX-5902 and effects on cell proliferation were measured by the Cell Titer-Glo assay. Using 100nM as a cutoff, 14 sensitive lines and 4 resistant lines were identified, with an average IC50 of 56 nM in the sensitive lines. Of these, we chose 2 sensitive lines (MDA-MB-231, HCC1806) and 2 resistant lines (MDA-MB-436 and CAL-120) and assessed induction of apoptosis by the Incucyte caspase activity assay. Robust induction of apoptosis was observed in both sensitive lines (N=3). These lines were then subjected to cell cycle analysis by flow cytometry, which revealed a pronounced G2/M cell cycle arrest and aneuploidy following exposure to RX-5902. Western blot analysis of the MDA-MB-231 cell line showed decreases in the Wnt pathway-related protein nuclear ß-catenin in doses ranging from 20 nM to 200 nM. Finally, the therapeutic efficacy of RX-5902 was assessed as a single agent and in combination with two immune-oncology agents in the treatment of the TNBC 4T1 animal model. RX-5902 as a single agent showed dose dependency in the 4T1 model, and when given in combination with either anti-CTLA4 or anti-PD1 showed an additive effect (p<0.001). All the treatments were well-tolerated and no severe body weight loss was observed in this study.

Conclusions: RX-5902 showed efficacy against several in vitro and in vivo preclinical models of TNBC. RX-5902 resulted in G2/M arrest and induced apoptosis in sensitive TNBC cell lines and decreases in nuclear beta-catenin. In vivo, RX-5902 demonstrated additive anti-tumor effects when combined with either anti-CTLA4 or anti-PD1 immunotherapies. Together, these finding indicate that RX-5902 may have important clinical implications for the treatment of TNBC. A phase 2a clinical study in metastatic TNBC is ongoing..training_cert

Citation Format: Tentler JJ, Frank JG, Kim DJ, George C, Lee YB, Ely B, Tan AC, Kim J, Pitts TM, Capasso A, Dailey KL, Eckhardt G, Diamond JR. Preclinical studies of RX-5902, a beta-catenin modulator in triple negative breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P5-21-16.

Abstract PD3-16: Clinical safety and efficacy of the aurora and angiogenic kinase inhibitor ENMD-2076 in previously treated, locally advanced or metastatic triple-negative breast cancer

Background: Triple-negative breast cancer (TNBC) is an aggressive breast cancer subtype defined by the lack of expression of the estrogen and progesterone receptors and lack of HER2 over-expression. ENMD-2076 is an orally bioavailable small molecule inhibitor of Aurora and angiogenic kinases with pro-apoptotic and antiproliferative activity in preclinical models of TNBC.

Methods: This two institution, single-arm, two-stage, phase II clinical trial enrolled patients with locally advanced or metastatic TNBC refractory to 1-3 prior lines of chemotherapy in the advanced setting. Patients had ECOG PS ≤ 1, measureable disease by RECIST 1.1 and no evidence of brain metastasis. Patients were treated with ENMD-2076 250 mg PO daily with continuous dosing in 4-week cycles until disease progression or unacceptable toxicity occurred. The primary end point was 6-month clinical benefit rate (6-CBR) and secondary endpoints included time to progression (TTP), PK profile, safety and biologic correlatives in archival and fresh serial tumor biopsies in a subset of patients.

Results: Between July 2012 and October 2016, 41 patients were enrolled (median age 54; range 30-73; female 40; male 1). Patients received a mean 1.7 prior lines of chemotherapy for locally advanced unresectable or metastatic disease and 80.5% received prior neoadjuvant or adjuvant chemotherapy (N=33). Thirty-six patients were evaluable per protocol for the primary efficacy analysis. Five patients (12.2%) were not included in the efficacy analysis due to: adverse events (AE) leading to discontinuation prior to objective efficacy assessment (N=3), not meeting eligibility criteria on day 1 (N=1) and withdraw of consent in cycle 1 (N=1). The study proceeded to the second stage of enrollment based on observing three 6-CBR events in Stage 1 (N=18 patients). The 6-CBR in the overall trial was 16.7% (95% exact CI: 6%-32.8%; 2 patients with PR and 4 patients with SD > 6 mos). The median duration of response or clinical benefit in these patients was 32 weeks (8 cycles). 4-CBR was 27.8% (95% exact CI: 14%-45.2%). Dose reduction occurred in 8 patients (20%) for fatigue, hypertension and proteinuria. The most common grade 3 treatment-related adverse events were hypertension (37.5%) and fatigue (10%). One patient experienced grade 4 hypertension. Analysis of serial tumor biopsies prior to and following 2 weeks of ENMD-2076 (N=8 patients), demonstrated a treatment-induced decrease in cellular proliferation (Ki-67) and microvessel density (CD34) as assessed by IHC. Immunofluorescence performed on a subset of samples demonstrated an increase in p53-family member expression following treatment, consistent with changes observed in preclinical TNBC patient-derived tumor xenograft models.

Conclusions: ENMD-2076 has durable clinical activity in a subset of patients with pretreated, advanced or metastatic triple-negative breast cancer. Predictive biomarker development using archival and fresh tumor tissue is underway. Exploration of lower doses of ENMD-2076 in future clinical trials may improve tolerability.

Citation Format: Diamond JR, Eckhardt SG, Pitts TM, van Bokhoven A, Aisner D, Gustafson DL, Capasso A, Elias AD, Storniolo AM, Schneider BP, Gao D, Tentler JJ, Borges VF, Miller KD. Clinical safety and efficacy of the aurora and angiogenic kinase inhibitor ENMD-2076 in previously treated, locally advanced or metastatic triple-negative breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr PD3-16.

Abstract P1-12-01: Withdrawn

This abstract was withdrawn by the authors.

Abstract B175: Rational combination of mTOR and Aurora kinase A inhibition in preclinical models of triple-negative breast cancer

Background: Alisertib is a highly selective inhibitor of Aurora kinase A and has antiproliferative and proapoptotic activity in a subset of triple-negative breast cancer (TNBC) cell lines and patient-derived tumor xenograft (PDX) models. Cellular senescence and increased expression of genes in the PI3K/AKT/mTOR pathway has been observed in TNBC models following treatment with alisertib that demonstrate de novo or acquired resistance. The purpose of this study was to investigate the combination of alisertib and the TORC1/2 inhibitor TAK-228 in preclinical TNBC models. Methods: MDA-MB-468, HCC1187, HCC1937, CAL51, and BT20 cells were plated in 96 well plates and exposed to increasing concentrations of alisertib (25nM-125nM), TAK-228 (25nM-125nM), or the combination and proliferation was assessed using the Cell Titer-Glo (CTG) assay. Apoptosis was assessed using long-term live cell microscopy and caspase 3/7 staining. Western blotting was used to assess changes in pS6, p4EBP1, and survivin expression. TNBC p53 wildtype CAL51 cells were transfected with the fluorescent ubiquitin cell cycle indicator (FUCCI) reporters and exposed to increasing concentrations of alisertib, TAK-228, or the combination to evaluate the effect on cell cycle progression, growth, and apoptosis. TNBC PDX models CU_TNBC_004 and CU_TNBC_007 were treated with vehicle, alisertib (30mg/kg), TAK-228 (0.5mg/kg), or the combination and assessed for tumor growth inhibition and translational markers by immunofluorescence (IF) and senescence-associated- ß-galactosidase (SA-ß-gal) staining. Results: A combination effect was observed for alisertib and TAK-228 in vitro with a decrease in cellular proliferation with the combination as measured by CTG. We observed an increase in cell death with the combination, as opposed to cell cycle arrest with single-agent treatment. Alisertib treatment was associated with an increase in survivin not observed with combination treatment. TAK-228 treatment was associated with a decrease in pS6 and p4EBP1 as a single agent or in combination. The combination of TAK-228 and alisertib resulted in greater tumor growth inhibition in vivo as compared to either single agent alone, accompanied by an increase in apoptosis as measured by BAX and DR5 expression and a decrease in senescence as evaluated by SA-ß-gal and phenotypic changes. Single agents in the CAL51 FUCCI system resulted in a dose-dependent effect on cell cycle progression and apoptosis by live cell microscopy. The combination, however, led to a complete block of cell growth and simultaneous apoptosis, leading to no expansion of cells after treatment and a gradual loss of the cell population. Conclusions: The combination of alisertib and TAK-228 in vitro and in vivo in TNBC models resulted in greater antiproliferative and proapoptotic activity. This combination is currently being investigated in a phase I dose escalation trial in patients with advanced solid tumors with a planned expansion cohort in metastatic TNBC to further evaluate the mechanism of the combination (NCT02719691).

Citation Format: Jennifer R. Diamond, James D. Orth, Anastasia Ionkina, Kyrie Dailey, Todd M. Pitts, Anna Capasso, Joshua M. Marcus, Russell T. Burke, Sarah L. Davis, Jiyhe Kim, Aik-Choon Tan, Sue G. Eckhardt, John J. Tentler. Rational combination of mTOR and Aurora kinase A inhibition in preclinical models of triple-negative breast cancer [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B175.

Abstract A083: A phase Ib study of the combination of MLN0128 (dual TORC1/2 inhibitor) and MLN8237 (Aurora A inhibitor, alisertib) in patients with advanced solid tumors

Background: MLN0128 is an oral inhibitor of mTOR kinase and mTORC1/2 signaling. Alisertib is an oral inhibitor of Aurora A kinase. Senescence and upregulation of genes in the PI3K/AKT/mTor pathway have been observed in triple-negative breast cancer (TNBC) patient-derived xenograft models treated with alisertib, with greater tumor growth inhibition demonstrated in combination with MLN0128 as compared to each agent alone. An investigator-initiated trial was developed to evaluate the combination of MLN0128 and alisertib in patients with advanced solid tumors, followed by an expansion cohort in metastatic TNBC and other selected cancers. The goals of this ongoing study are to evaluate safety, tolerability, pharmacokinetics (PK) and preliminary efficacy of the combination. Results of dose escalation are presented here. Methods: Patients with advanced solid tumors refractory to standard therapy were treated orally at escalating doses with the combination of MLN0128 daily on a continuous schedule and alisertib twice daily (BID) on days 1-7 of a 21-day cycle. Dose escalation was conducted according to a standard 3+3 design. Key eligibility criteria included HgbA1c <7%, fasting serum glucose <130mg/dL and fasting triglycerides <300mg/dL, normal cardiac function, no condition with potential to cause excessive daytime sleepiness (including chronic hypoxia) and no risk of malabsorption of oral medications. PK assessments were performed at various time points after single-agent and combination dosing. Results: A total of 16 patients with refractory cancers were enrolled in dose escalation. No dose-limiting toxicity (DLT) was observed in dose level 1 (MLN0128 1mg/alisertib 30mg) or dose level 2 (2mg/30mg). At the third dose level (2mg/40mg) 2 of 7 patients experienced a DLT (grade 3 fatigue/confusion and grade 2 GERD/nausea leading to study discontinuation). In an alternate dose level cohort evaluating MLN0128 3mg and alisertib 30mg, 2 of 2 patients experienced a DLT of grade 3 fatigue. The maximum tolerated dose (MTD) of the combination was determined to be MLN0128 2mg daily and alisertib 30mg BID. Most common adverse events (AEs) of any grade included alopecia, diarrhea, fatigue and rash in 19% each and nausea in 31% of patients. Most common Grade 3 AEs included fatigue (19%) and decreased neutrophil count (31%). Dose modification was required in 56% of patients, most often due to neutropenia. Median time on study was 3 cycles (range 1-15) at data cutoff. Best response of stable disease was observed in 5 patients (31%), with prolonged stable disease noted in a patient with ER+/HER2- breast cancer (15 cycles) and a patient with castrate-resistant prostate cancer (10 cycles). PK assessments indicate no significant drug interaction between agents. Cmax was 24.7 (± 13.6) ng/mL for MLN0128 and 1049 (±363) ng/mL for alisertib at combination MTD doses. MLN0128 AUC was 128.2 (±72.7) ng/mLxhr and alisertib AUC0-8 was 6119 (±2331) ng/mlxhr at these doses. Conclusions: MLN0128 2mg daily on a continuous schedule and alisertib 30mg BID days 1-7 of a 21-day cycle is the MTD of the drug combination. An expansion cohort in patients with TNBC and other selected cancers is currently enrolling at this dose. Functional imaging and serial tumor biopsies are being integrated into this cohort to assess the pharmacodynamic interactions of the combination.

Citation Format: S. Lindsey Davis, Elaine T. Lam, Bradley R. Corr, Cindy L. O'Bryant, Ashley Glode, Nichole Adler, Todd M. Pitts, John J. Tentler, Anna Capasso, Kyrie Dailey, Natalie J. Serkova, Colin D. Weekes, Daniel L. Gustafson, Christopher H. Lieu, Wells A. Messersmith, Stephen Leong, S. Gail Eckhardt, Jennifer R. Diamond. A phase Ib study of the combination of MLN0128 (dual TORC1/2 inhibitor) and MLN8237 (Aurora A inhibitor, alisertib) in patients with advanced solid tumors [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A083.

Efficacy and Molecular Mechanisms of Differentiated Response to the Aurora and Angiogenic Kinase Inhibitor ENMD-2076 in Preclinical Models of p53-Mutated Triple-Negative Breast Cancer

Purpose

Triple-negative breast cancer (TNBC) is a subtype associated with poor prognosis and for which there are limited therapeutic options. The purpose of this study was to evaluate the efficacy of ENMD-2076 in p53-mutated TNBC patient-derived xenograft (PDX) models and describe patterns of terminal cell fate in models demonstrating sensitivity, intrinsic resistance, and acquired resistance to ENMD-2076.

Experimental design

p53-mutated, TNBC PDX models were treated with ENMD-2076 and evaluated for mechanisms of sensitivity or resistance to treatment. Correlative tissue testing was performed on tumor tissue to assess for markers of proliferation, apoptosis, senescence, and pathways of resistance after treatment and at the time of acquired resistance.

Results

Sensitivity to ENMD-2076 200 mg/kg daily was associated with induction of apoptosis while models exhibiting intrinsic or acquired resistance to treatment presented with a senescent phenotype. Response to ENMD-2076 was accompanied by an increase in p53 and p73 levels, even within the background of mutant p53. Treatment with ENMD-2076 resulted in a decrease in pAurA and an increase in pHH3. We observed a TNBC subtype switch from the luminal androgen receptor to the basal-like subtype at acquired resistance.

Conclusion

ENMD-2076 has antitumor activity in preclinical models of p53-mutated TNBC. Increased levels of p53 and p73 correlated with sensitivity whereas senescence was associated with resistance to ENMD-2076. The novel finding of a TNBC subtype switch at time of acquired resistance may provide mechanistic insights into the biologic effects of selective pressure of anticancer treatments on TNBC. ENMD-2076 is currently being evaluated in a Phase 2 clinical trial in patients with metastatic, previously treated TNBC where these biologic correlates can be further explored.

Efficacy and Safety of Anti-Trop-2 Antibody Drug Conjugate Sacituzumab Govitecan (IMMU-132) in Heavily Pretreated Patients With Metastatic Triple-Negative Breast Cancer

Purpose Trop-2, expressed in most triple-negative breast cancers (TNBCs), may be a potential target for antibody-drug conjugates. Sacituzumab govitecan, an antibody-drug conjugate, targets Trop-2 for the selective delivery of SN-38, the active metabolite of irinotecan. Patients and Methods We evaluated sacituzumab govitecan in a single-arm, multicenter trial in patients with relapsed/refractory metastatic TNBC who received a 10 mg/kg starting dose on days 1 and 8 of 21-day repeated cycles. The primary end points were safety and objective response rate; secondary end points were progression-free survival and overall survival. Results In 69 patients who received a median of five prior therapies (range, one to 12) since diagnosis, the confirmed objective response rate was 30% (partial response, n = 19; complete response, n = 2), the median response duration was 8.9 (95% CI, 6.1 to 11.3) months, and the clinical benefit rate (complete response + partial response + stable disease ≥ 6 months) was 46%. These responses occurred early, with a median onset of 1.9 months. Median progression-free survival was 6.0 (95% CI, 5.0 to 7.3) months, and median overall survival was 16.6 (95% CI, 11.1 to 20.6) months. Grade ≥ 3 adverse events included neutropenia (39%), leukopenia (16%), anemia (14%), and diarrhea (13%); the incidence of febrile neutropenia was 7%. The majority of archival tumor specimens (88%) were moderately to strongly positive for Trop-2 by immunohistochemistry. No neutralizing antibodies to the ADC or antibody were detected, despite repeated cycles developed. Conclusion Sacituzumab govitecan was well tolerated and induced early and durable responses in heavily pretreated patients with metastatic TNBC. As a therapeutic target and predictive biomarker, Trop-2 warrants further research.

Phase Ib study of the mitochondrial inhibitor ME-344 plus topotecan in patients with previously treated, locally advanced or metastatic small cell lung, ovarian and cervical cancers

Background This multicenter, open-label, phase Ib study was designed to assess the safety, pharmacokinetics and preliminary efficacy of ME-344, a mitochondrial inhibitor, administered in combination with the topoisomerase I inhibitor, topotecan, in patients with previously treated, locally advanced or metastatic small cell lung (SCLC), ovarian and cervical cancers. Patients and methods In Part 1, patients received ME-344 10 mg/kg intravenously weekly on days 1, 8, 15 and 22 in combination with topotecan 4 mg/m² on days 1, 8, and 15 of a 28 day cycle. Cycles were repeated until disease progression or unacceptable toxicity. Patients were evaluated for dose-limiting toxicity (DLT) in cycle 1 and ME-344 pharmacokinetic samples were obtained. In Part 2, patients with locally advanced or metastatic SCLC and ovarian cancer were enrolled in expansion cohorts treated at the recommended phase II dose (RP2D) determined in Part 1. Results Fourteen patients were enrolled in Part 1 and no DLTs were observed. The RP2D of ME-344 in combination with topotecan was established as 10 mg/kg. In Part 2, 32 patients were enrolled. The most common treatment-emergent all-grade and grade 3/4 toxicities included fatigue (65.2%, 6.5%), neutropenia (56.5%, 43.5%) and thrombocytopenia (50%, 23.9%). One patient with recurrent ovarian cancer experienced a partial response by RECIST 1.1 and 21 patients achieved stable disease as best response. Conclusions The combination of ME-344 10 mg/kg weekly and topotecan 4 mg/m² was tolerable, however, the degree of anti-cancer activity does not support further investigation of the combination in unselected patients with SCLC, ovarian and cervical cancers.