On April 12, 2021 PharmAbcine Inc. (KOSDAQ: 208340ks), a clinical-stage biotech company focusing on the development of antibody therapeutics, reported that the company presented an e-poster featuring the non-clinical data of PMC-309 at American Association for Cancer Research (AACR) (Free AACR Whitepaper) 2021 Annual Meeting taking place virtually (Press release, PharmAbcine, APR 12, 2021, View Source [SID1234577940]).

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PMC-309, one of the company’s first immuno-oncology drug candidates, is a monoclonal IgG (Immunoglobulin G) that targets human VISTA (V-domain Ig Suppressor of T cell Activation), an immune checkpoint regulator. VISTA is found overexpressed on MDSC (Myeloid-Derived Suppressor Cells) and M2 macrophages both of which are immunosuppressive cells found abundantly around TME (Tumor Microenvironment).

The presentation highlighted that PMC-309 inhibits VISTA pathway on immunosuppressive cells and increases T cell activities in in vitro settings and shows potent anti-tumor effects in in vivo studies.

The in vitro studies confirmed that PMC-309 inhibits VISTA interaction and promotes T cell activation. PMC-309 blocked the VISTA pathway with its partner molecules such as VSIG3 (V-Set and Immunoglobulin domain containing 3), PSGL1 (P-selectin glycoprotein ligand-1) and other VISTA. In addition, there was a rise in the level of IFN-y, a pro-inflammatory cytokine, which indicates that PMC-309 enhanced T cell activities.

In in vivo studies, the test subjects administered with PMC-309 in both hPBMC (human Peripheral Blood Mononuclear Cell) engrafted mouse model and human VISTA Knock-In mouse model showed notable tumor growth inhibition. PMC-309 also showed a possible synergistic effect when used in combo with an anti-PD1 antibody because the combination of two antibodies demonstrated significantly improved tumor growth inhibition.

"Our non-clinical studies revealed PMC-309’s unique binding mechanism and its anti-tumor effect," said Dr. Jin-San Yoo, CEO of PharmAbcine. "The study results add to our confidence that PMC-309 can be a promising immunotherapeutic strategy in both mono and combo therapies for patients who do not respond to other immuno-oncology drugs."

Dr. Yoo also added, "We plan to initiate the IND (Investigational New Drug)-enabling studies and evaluate the potential toxicity risk this year. We expect PMC-309 to enter a clinical stage in 2022."

The e-poster presentation is currently available on the AACR (Free AACR Whitepaper) website. The details of the presentation are as follows:

Title: PMC309, a highly selective anti-VISTA antibody enhances T cell activation through blocking the interaction of T cells and myeloid derived suppressor cells (MDSC)
Session category/title: Immunology/Immune Checkpoints
Abstract number: 1116
Poster number: 1626
Presentation Type: E-poster with audio presentation

On April 12, 2021 GT Biopharma, Inc. (NASDAQ: GTBP), a clinical stage immuno-oncology company focused on developing innovative therapeutics based on the Company’s proprietary NK cell engager (TriKE) protein biologic technology platform, reported additional interim results from its GTB-3550 TriKE first-in-human Phase I/II clinical trial for the treatment of high-risk myelodysplastic syndromes (MDS) and refractory/relapsed acute myeloid leukemia (AML) (Press release, GT Biopharma, APR 12, 2021, View Source [SID1234577939]).

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Additional results show GTB-3550 TriKE monotherapy is able to rescue the patient’s otherwise exhausted/inhibited/non-functional endogenous NK cell population and target direct killing of the patient’s AML and MDS cancer cells without the need for the co-administration addition of supplemental progenitor-derived or autologous/allogenic engineered NK cells.

GTB-3550 TriKE monotherapy has demonstrated clinical benefit in very hard to treat relapsed/refractory AML and high-risk MDS cancer patients by significantly reducing cancer cell (blast) levels and, in some cases, ending transfusion dependency with patients becoming eligible for bone marrow transplant.

The ability to use GTB-3550 in a monotherapy setting is a significant competitive and therapeutic advantage, and a major cost savings compared to the co-administration of drug/cell therapy combination regimens. GTB-3550 TriKE therapy requires no patient pre-treatment regimens such as myeloablative chemotherapy, and is well tolerated with no signs of cytokine release syndrome (CRS) or other toxicities suggesting GTB-3550 could be used to treat patients earlier in the disease process, whereas complicated and expensive combination drug/cell therapy regimens are expected to be used as late-stage or salvage therapies after all other therapeutic options have been exhausted.

Highlights from the first nine patients treated with GTB-3550 TriKE include:

Up to 63.7% Reduction in Bone Marrow Blast Levels Resulting in Clinical Benefit
Restores Patient’s Endogenous NK Cell Function, Proliferation and Immune Surveillance
No Progenitor-derived or Autologous/Allogenic Cell Therapy Required
No Cytokine Release Syndrome Observed
3 out of the last 5 Patients Treated Respond (25mcg/kg/day to 100mcg/kg/day therapeutic dose range)
"We believe GTB-3550 TriKE sets a new standard for NK cell engager therapies due to the incorporation of Interleukin 15 (IL-15) directly in the protein backbone. The flexibility and versatility of our TriKE platform allows us to change the cancer cell targeting moiety of TriKE to attack different cancers while maintaining the core NK cell activation, proliferation and persistence attributes of the molecule," said Anthony J. Cataldo, GT Biopharma’s Chairman and Chief Executive Officer. "The TriKE is a true monotherapy, unlike all other NK cell technologies in development. The novel TriKE uniquely does not need any outside NK cell manufacturing or combination drugs, to supplement or assist. Further, the TriKE does not require pre-conditioning of the patient’s immune system. These supplemental requirements of competitive technologies add tremendous cost to an already costly therapeutic approach. Everything the TriKE does happens with no outside assistance whatsoever. We believe the TriKE’s clinical data is demonstrating exactly that, opening the door to a significantly more cost-effective off-the-shelf therapeutic."

About High-Risk Myelodysplastic Syndromes
MDS is a rare form of bone marrow-related cancer caused by irregular blood cell production within the bone marrow. As a result of this irregular production, MDS patients do not have sufficient normal red blood cells, white blood cells and/or platelets in circulation. High-risk MDS is associated with poor prognosis, diminished quality of life, and a higher chance of transformation to acute myeloid leukemia. Approximately 40% of patients with high-risk MDS transform to AML, another aggressive cancer with poor outcomes.

About Acute Myeloid Leukemia
Acute myeloid leukemia is a type of cancer in which the bone marrow makes abnormal myeloblasts (a type of white blood cell), red blood cells, or platelets. According to the National Cancer Institute (NCI), the five-year survival rate is about 35% in people under 60 years old, and 10% in people over 60 years old. Older people whose health is too poor for intensive chemotherapy have a typical survival of five to ten months. AML accounts for roughly 1.8% of cancer deaths in the United States.

About GTB-3550 TriKE
GTB-3550 is the Company’s first TriKE product candidate being initially developed for the treatment of AML and MDS, and other CD33+ hematologic cancers. GTB-3550 is a single-chain, tri-specific scFv recombinant fusion protein conjugate composed of the variable regions of the heavy and light chains of anti-CD16 and anti-CD33 antibodies and a modified form of Interleukin 15 (IL-15). The natural killer (NK) cell-stimulating cytokine human IL-15 portion of the molecule provides a self-sustaining signal that activates NK cells and enhances their ability to kill. We intend to study GTB-3550 in CD33 positive leukemias such as acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), and other CD33+ hematopoietic malignancies.

About GTB-3550 TriKE Clinical Trial
Patients with CD33+ malignancies (primary induction failure or relapsed AML with failure of one reinduction attempt or high-risk MDS progressed on two lines of therapy) age 18 and older are eligible (NCT03214666). The primary endpoint is to identify the maximum tolerated dose (MTD) of GTB-3550 TriKE. Correlative objectives include the number, phenotype, activation status and function of NK cells and T cells.

On April 12, 2021 Innovent Biologics, Inc. ("Innovent", HKEX: 01801), a world-class biopharmaceutical company that develops, manufactures and commercializes high-quality medicines for the treatment of cancer, metabolic, autoimmune and other major diseases, reported with Eli Lilly and Company ("Lilly",NYSE: LLY) that the results of the Phase 3 ORIENT-3 study were released today in an oral presentation at the American Association for Cancer Research (AACR) (Free AACR Whitepaper) Annual Meeting 2021 (Press release, Innovent Biologics, APR 12, 2021, View Source [SID1234577938]).

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ORIENT-3 is a randomized, open-label, Phase 3 clinical trial evaluating TYVYT (sintilimab injection) versus docetaxel as a second-line treatment for advanced or metastatic squamous non-small cell lung cancer (sqNSCLC). A total of 290 patients whose cancer had progressed following first-line treatment with platinum-based chemotherapy were enrolled. Based on the primary analysis population (280 patients, excluding patients on the docetaxel arm who received immunotherapy prior to disease progression), TYVYT (sintilimab injection) demonstrated a statistically significant improvement in overall survival (OS) compared to docetaxel, meeting the pre-specified primary endpoint. The median OS was 11.79 months for patients on the TYVYT (sintilimab injection) arm and 8.25 months for those on the docetaxel arm (HR=0.74, 95% CI: 0.56-0.96, P=0.02489). The median progression-free survival (PFS) as assessed by investigators was 4.30 months versus 2.79 months (HR=0.52, 95% CI: 0.39-0.68, P<0.00001), and the confirmed objective response rate (ORR) was 25.5 percent versus 2.2 percent (P<0.00001), respectively. Safety was consistent with previous studies of TYVYT (sintilimab injection), and no new safety signals were identified.

Professor Yuankai Shi, principal investigator of ORIENT-3, Associate Dean of Cancer Hospital, Chinese Academy of Medical Sciences and Chairman of Cancer Foundation of China, stated: "Lung cancer is the leading cause of cancer death globally, of which non-small cell lung cancer accounts for 80 to 85 percent. In the past few decades, drug development of non-small cell lung cancer has mainly focused on nonsquamous non-small cell lung cancer, while drug development of squamous non-small cell lung cancer has been slower due to its unique epidemiological, histopathological and molecular characteristics. In China, specifically, the approved options for second-line immunotherapy to treat squamous non-small cell lung cancer are even more limited. The ORIENT-3 study showed that the anti-PD-1 monoclonal antibody sintilimab significantly improved overall survival for the second-line treatment of squamous non-small cell lung cancer patients, which is of great clinical value. We hope that the positive results of ORIENT-3 can help more squamous non-small cell lung cancer patients."

"TYVYT (sintilimab injection) was the first anti-PD-1 inhibitor included in the New Catalogue of the National Reimbursement Drug List in 2019," said Dr. Hui Zhou, Vice President of Medical Science and Strategy Oncology of Innovent. "In August 2020, the NMPA accepted a new indication application for TYVYT (sintilimab injection) in combination with chemotherapy for first-line treatment of squamous NSCLC. In the ORIENT-3 study, sintilimab as second-line monotherapy demonstrated a significantly improved survival benefit for patients with advanced squamous non-small cell lung cancer, and we look forward to the potential approval of this indication, to help more patients with this type of lung cancer."

"We are excited about these results, showing TYVYT (sintilimab injection) significantly improved overall survival in this patient population. This study underscores the joint commitment from Lilly and Innovent to provide innovative treatment options to patients with lung cancer," said Dr. Wang Li, Senior Vice President of Lilly China and Head of Lilly China Drug Development and Medical Affairs. "We would like to thank the patients, the investigators, the clinical trial centers and our colleagues from Innovent that are involved in the study. We look forward to working together to potentially bring this new treatment option to people in China with squamous non-small cell lung cancer."

About Squamous NSCLC

Lung cancer is a malignancy with the highest morbidity and mortality in China. NSCLC accounts for about 80 to 85 percent of lung cancer. Approximately 70 percent of people with NSCLC have locally advanced or metastatic NSCLC at initial diagnosis, rendering many of those patients with no chance of radical resection. Meanwhile, even after radical surgery, patients still have a high chance of recurrence and eventually die from disease progression. About 30 percent of people in China with non-small cell lung cancer have tumors of the squamous subtype and there are limited approved second-line therapies for these patients. Therefore, there remains a huge unmet medical need in China.

About the ORIENT-3 Trial

ORIENT-3 is a randomized, open-label, multi-center, Phase 3 clinical trial to evaluate the efficacy and safety of TYVYT (sintilimab injection) as second-line therapy for advanced or metastatic sqNSCLC (ClinicalTrials.gov, NCT 03150875). The primary endpoint is overall survival (OS). The secondary endpoints include progression-free survival (PFS) as assessed by investigators based on RECIST v1.1, objective response rate (ORR) and safety profile.

A total of 290 patients were enrolled in ORIENT-3 and randomized in a 1:1 ratio to receive either TYVYT (sintilimab injection) 200mg or docetaxel every three weeks. The patients received treatment until radiographic disease progression, unacceptable toxicity or any other conditions that require treatment discontinuation.

About TYVYT (Sintilimab Injection)

TYVYT (sintilimab injection), an innovative drug with global quality standards jointly developed in China by Innovent and Lilly, has been granted marketing approval by the NMPA (National Medical Products Administration) for the treatment of relapsed or refractory classic Hodgkin’s lymphoma after two lines or later of systemic chemotherapy, and is included in the 2019 Guidelines of Chinese Society of Clinical Oncology for Lymphoid Malignancies. In February 2021, TYVYT (sintilimab injection) was approved by the China NMPA in combination with pemetrexed and platinum chemotherapy as first-line therapy for the treatment of nonsquamous non-small cell lung cancer. TYVYT (sintilimab injection) was included in the National Reimbursement Drug List (NRDL) in November 2019 as the first PD-1 inhibitor and the only PD-1 included in the list in that year.

Currently TYVYT (sintilimab injection) has three supplemental New Drug Applications ("sNDA") under review by the NMPA. In August 2020, the NMPA accepted the sNDA for TYVYT (sintilimab injection) in combination with gemcitabine and platinum chemotherapy as first-line therapy in squamous NSCLC. In January 2021, the NMPA accepted the sNDA for TYVYT (sintilimab injection) in combination with BYVASDA (bevacizumab injection) as first-line therapy in Hepatocellular Carcinoma (HCC) and the sNDA for TYVYT (sintilimab injection) as second-line therapy in squamous NSCLC. Besides, in May 2020, TYVYT (sintilimab injection) monotherapy met the primary endpoint of overall survival in the Phase 2 ORIENT-2 study as second-line therapy in patients with advanced or metastatic esophageal squamous cell carcinoma.

TYVYT (sintilimab injection), is a type of immunoglobulin G4 monoclonal antibody, which binds to PD-1 molecules on the surface of T-cells, blocks the PD-1 / PD-Ligand 1 (PD-L1) pathway and reactivates T-cells to kill cancer cells. Innovent is currently conducting more than 20 clinical studies with TYVYT (sintilimab injection) to evaluate its safety and efficacy in a wide variety of cancer indications, including more than 10 registrational or pivotal clinical trials. Meanwhile, Innovent is conducting clinical research studies on TYVYT (sintilimab injection) worldwide.

On April 12, 2021 Antengene Corporation Limited ("Antengene", SEHK: 6996.HK), a leading innovative biopharmaceutical company dedicated to discovering, developing, and commercializing global first-in-class and/or best-in-class therapeutics in hematology and oncology, reported preclinical data at the American Association for Cancer Research (AACR) (Free AACR Whitepaper) Annual Meeting 2021, which demonstrated the synergistic effect of the combination of ATG-010 (selinexor, XPO1 inhibitor) and ATG-008 (onatasertib, mTORC1/2 inhibitor) for the treatment of triple-hit diffuse large B-cell lymphoma (DLBCL) (Press release, Antengene, APR 12, 2021, View Source [SID1234577937]).

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#1380: Synergistic effect of the combination of XPO1 and mTORC1/2 inhibition for the treatment of triple-hit DLBCL
Results from this study demonstrated potent in vitro and in vivo anti-tumor efficacy and synergy with the combination of ATG-010 and ATG-008, including strong synergistic activities in the triple-hit DLBCL cell line. Meanwhile, in the DLBCL circulating tumor cell-derived explants (CDX) model, the combination of ATG-010 and ATG-008 also showed enhanced tumor growth inhibition and synergism.

The single agent oral XPO1 inhibitor, ATG-010, is a first-in-class and only-in-class selective inhibitor of nuclear export (SINE) compound, approved by the US Food and Drug Administration (FDA) for the treatment of patients with DLBCL after at least two prior therapies. ATG-008 is a dual mTORC1/2 kinase inhibitor, which has shown preclinical and clinical activity in treating DLBCL. Antengene is currently developing a clinical study to investigate the combination of ATG-010 and ATG-008 in relapsed or refractory DLBCL (the MATCH trial).

The preclinical data showed:

ATG-008 and ATG-010 both inhibit the growth of the DLBCL cell line in vitro.
ATG-008 combined with ATG-010 enhanced the growth inhibition of triple-hit DLBCL cells.
ATG-008 combined with ATG-010 showed in vitro synergism in triple-hit DLBCL cells.
ATG-008 combined with ATG-010 showed in vivo synergism in CDX of the triple-hit DLBCL cell line.
Dr. Jay Mei, Founder, Chairman and CEO of Antengene, commented: "ATG-010 has been approved for the treatment of relapsed or refractory DLBCL, whilst ATG-008 has shown early clinical activity in the same disease. Using in vitro and in vivo DLBCL models, we found that ATG-010 combined with ATG-008 at certain concentrations could achieve amplified anti-tumor activity in triple-hit DLBCL. The strong synergism of the ATG-010 plus ATG-008 combination suggests a promising therapeutic strategy for the treatment of patients with DLBCL, including triple-hit disease where significant unmet medical needs exist, that we are looking forward to exploring in the MATCH trial."

On April 12, 2021 Ascentage Pharma (6855.HK), a globally focused, clinical-stage biotechnology company engaged in developing novel therapies for cancers, chronic hepatitis B (CHB), and age-related diseases, reported the preclinical results of five of the company’s novel drug candidates at the American Association for Cancer Research (AACR) (Free AACR Whitepaper) Annual Meeting 2021 (Press release, Ascentage Pharma, APR 12, 2021, View Source [SID1234577936]). These studies are from seven preclinical studies in various tumor types and have signified the therapeutic potential of multiple combination therapies in cancer.

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The AACR (Free AACR Whitepaper) annual meeting is one of the world’s largest and long-standing scientific gatherings in the field of cancer research. Covering some of the most cutting-edge advances in all the areas of oncology research and innovation, the annual event attracts tremendous interest from the global cancer research community.

Results from the seven preclinical studies selected for poster presentations at this year’s AACR (Free AACR Whitepaper) annual meeting include:

Candidate

Title

Abstract#

HQP1351

FMS-like tyrosine kinase 3 (FLT3) inhibition by olverembatinib (HQP1351) downregulates MCL-1 and synergizes with BCL-2 inhibitor APG-2575 in preclinical models of FLT3-mutant acute myeloid leukemia (AML)

1096

ATP-site inhibitor olverembatinib, HQP1351, enhanced the effect of allosteric inhibitor on the resistance conferred by the compound mutations of BCR-ABL

1463

APG-2575

BCL-2 inhibitor APG-2575 and homoharringtonine (HHT) synergistically induces apoptosis and inhibits tumor growth in preclinical models of acute myeloid leukemia and myelodysplastic syndromes (AML/MDS)

981

Inhibition of BCL-2 (by APG-2575) and CDK4/6 synergistically induces cell cycle arrest and apoptosis in ER⁺ breast cancer

976

APG-1387

Therapeutic potential of inhibitor of apoptosis protein (IAP) inhibitor APG-1387 combined with DR5 agonist monoclonal antibody (mAb) CTB-006 in preclinical models of solid tumors

1924

APG-1252

Targeting BCL-xL addiction with APG-1252 (pelcitoclax) to overcome apoptotic blockade in neuroendocrine neoplasm (NEN)

984

APG-2449

Focal adhesion kinase (FAK) inhibitor APG-2449 sensitizes ovarian tumors to chemotherapy via CD44 downregulation

968

"These results presented at this year’s AACR (Free AACR Whitepaper) Annual Meeting are a testament to our continuous effort to address existing unmet medical needs, and provide strong scientific rationale for further investigations of our core drug candidates in combinations with therapies of other mechanism of actions and targeted pathways," said Dr. Yifan Zhai, Chief Medical Officer of Ascentage Pharma. "Combination therapy is playing an increasingly important role in cancer treatment. We will strive to make more progress of our core drug candidates and to hopefully bring these potential therapeutics to patients as early as possible."

FMS-like tyrosine kinase 3 (FLT3) inhibition by olverembatinib (HQP1351) downregulates MCL-1 and synergizes with BCL-2 inhibitor APG-2575 in preclinical models of FLT3-mutant acute myeloid leukemia (AML)

Abstract/Poster Number: 1096
Background
AML accounts for 80% of acute leukemias in adults. FLT3 gene mutations are observed in approximately 30% of patients with AML and augur a poor prognosis. Despite antitumor effects of selective FLT3 inhibitors, resistance to these agents continues to pose a formidable clinical challenge. The expression of pro-survival protein BCL-2 is frequently dysregulated, conferring resistance to FLT3 inhibitors, in AML. In this study, we explored the combination of clinical stage multikinase inhibitor HQP1351 (which also targets FLT3) and BCL-2-selective inhibitor APG-2575 in preclinical models of FLT3-mutant AML.

Conclusion
Taken together, our data suggest that FLT3 inhibition by HQP1351 downregulates MCL-1 and synergizes with BCL-2 inhibitor APG-2575 to potentiate cellular apoptosis in FLT3-mutant AML. The results provide scientific rationale for clinical development of HQP1351 combined with APG-2575 in patients with FLT3-ITD-mutant AML.

ATP-site inhibitor olverembatinib, HQP1351, enhanced the effect of allosteric inhibitor on the resistance conferred by the compound mutations of BCR-ABL

Abstract/Poster Number: 1463
Background
Treatment with tyrosine kinase inhibitors (TKIs) directed against the ATP-binding site of BCR-ABL promotes recovery of Ph+ leukemia. However, emergence of gatekeeper mutation T315I and compound mutants confer resistance to these TKIs. The allosteric inhibitor, asciminib, effectively inhibits BCR-ABL kinase through binding to the myristoyl-binding site. Combining asciminib with ponatinib can overcome only a subset of the resistance caused by BCR-ABL compound mutants. Olverembatinib (HQP1351) is a new generation TKI targeting BCR-ABL and currently in development for r/r CML. The purpose of this study is to evaluate whether a novel combination of olverembatinib and asciminib, targeting both ATP pocket and allosteric region of BCR-ABL protein, can promote the inhibitory effect on the kinase harboring compound mutations.

Conclusion
Our results demonstrated that the combination of ATP binding site inhibitor olverembatinib and allosteric inhibitor have synergistic anti-tumor effect on tumor cells harboring single or compound mutations in BCR-ABL. This novel strategy may help to overcome the secondary compound mutations post the treatment with TKIs.

BCL-2 inhibitor APG-2575 and homoharringtonine (HHT) synergistically induces apoptosis and inhibits tumor growth in preclinical models of acute myeloid leukemia and myelodysplastic syndromes (AML/MDS)

Abstract/Poster Number: 981
Background
The AML treatment landscape has improved dramatically in the past decade, with improved objective response rates and overall survival after treatment with newly approved targeted therapies. BCL-2 inhibition combined with a hypomethylating agent or low-dose cytosine arabinoside (Ara-C) is also effective in previously untreated elderly patients who are not candidates for standard induction therapy. However, the effect of BCL-2 inhibition is commonly weakened when tumor cells upregulate antiapoptotic protein MCL-1 to escape apoptosis. Thus, combination therapy is introduced to suppress MCL-1 levels. HHT (omacetaxine mepesuccinate) has been widely used in Chinese patients with AML for 30 years. As an inhibitor of protein synthesis, HHT decreases MCL-1. This study investigated the effect of combining clinical stage BCL-2 selective inhibitor APG-2575 with HHT in AML and MDS cells, as well as murine xenograft tumor models.

Conclusion
In summary, APG-2575 synergizes with HHT to potentiate antitumor activity in preclinical models of AML/MDS. HHT suppresses MCL-1 protein, preventing or abolishing formation of MCL-1:BIM, MCL-1:PUMA, and MCL-1:BAK complexes, and hence allowing prodeath proteins to fully engage in tumor cell apoptosis induction. Our results provide scientific rationale for clinical development of APG-2575 plus HHT in patients with AML/MDS.

Inhibition of BCL-2 (by APG-2575) and CDK4/6 synergistically induces cell cycle arrest and apoptosis in ER⁺ breast cancer

Abstract/Poster Number: 976
Background
Estrogen receptor positive (ER⁺)/human epidermal growth factor receptor 2 negative (HER2-) tumors represent the most common subset (about 75%) of all breast cancer cases. Combination treatment with endocrine therapy and a CDK4/6 inhibitor (CDK4/6i) is now the standard of care in early metastatic ER+ breast cancer. However, relapse or resistance to such combination therapy nearly inevitably occurs. Antiapoptotic protein BCL-2 is overexpressed in most cases of primary and metastatic ER+ breast cancer. We have shown that clinical-stage BCL-2 selective inhibitor APG-2575 enhances antitumor activity when combined with palbociclib in ER⁺ breast cancer xenograft models, including malignancies that are resistant to tamoxifen or progress after CDK4/6i treatment. We investigated mechanisms of action (MOAs) for synergistic effects of this combination.

Conclusion
Taken together, palbociclib drives breast cancer cells into a senescent state, and APG-2575 potentiates this antitumor effect by inducing cellular apoptosis. When combined with APG-2575, palbociclib inhibits MCL-1 expression and MCL-1:BIM complex formation as results of BCL-2 inhibition. Therefore, palbociclib reduces the threshold for apoptosis, while APG-2575 induces apoptosis by disrupting BCL-2:BIM complexes as well as enhancing expression of BIM and Noxa. Similar to palbociclib, APG-2575 also causes cell cycle arrest, and both agents collaboratively induce apoptosis in the combination setting. Our data reveal a viable MOA for synergistic effects, strengthening the scientific rationale for clinical development of the combination of the BCL-2 selective inhibitor APG-2575 and CDK4/6i palbociclib-based therapy in patients with ER+/HER2− breast cancer.

Therapeutic potential of inhibitor of apoptosis protein (IAP) inhibitor APG-1387 combined with DR5 agonist monoclonal antibody (mAb) CTB-006 in preclinical models of solid tumors

Abstract/Poster Number: 1924
Background
TNF-related apoptosis-inducing ligand (TRAIL) receptor (DR4 or DR5) agonists are promising agents for cancer therapy because they induce apoptosis selectively in cancer cells. However, their clinical effect is hampered by either primary or acquired resistance in cancer cells. Second mitochondria-derived activator of caspase (Smac) mimetics that antagonize the IAPs potently sensitize cancer cells to TRAIL-induced apoptosis in a caspase-8-dependent manner. We evaluated antitumor effects of small-molecule IAP antagonist APG-1387combined with an agonist mouse mAb directed against TRAIL death receptor type 5 (DR5) termed CTB-006 in the preclinical setting. Both agents are in phase I/II clinical development for patients with solid tumors.

Conclusion
In summary, our results suggest great potential of combination therapy with APG-1387 and CTB-006 for solid tumor therapy and deserves further clinical investigation.

Targeting BCL-xL addiction with APG-1252 (pelcitoclax) to overcome apoptotic blockade in neuroendocrine neoplasm (NEN)

Abstract/Poster Number: 984
Background
Current targeted therapies such as VEGFR inhibitor sunitinib and mTOR inhibitor everolimus extend progression-free survival (PFS) in patients with Grade 1 (G1) and G2 neuroendocrine tumors (NET), but the objective response rate remains low. The median PFS in patients with advanced neuroendocrine carcinoma (NEC) receiving platinum-based therapy is only 3 to 4 months. Hence, more effective therapy is needed to improve clinical outcomes. This study explored if BCL-2 family antideath proteins play a role in NEN tumorigenesis and whether clinical-stage dual BCL-2/BCL-xL inhibitor APG-1252 might overcome intrinsic apoptotic blockade in NEN.

Conclusion
In summary, the results suggest that BCL-xL plays an important role in NEN. Cellular sensitivity to BCL-2/BCL-xL inhibitor APG-1252-M1 correlates with baseline BCL-xL complex levels. In NEN patient samples, MCL-1 was also highly expressed, implicating its potential negative regulatory effect on sensitivity to APG-1252. Concurrent expression of BCL-xL and MCL-1 proteins suggests that a combination treatment targeting both proteins might be more effective in NEN. Our findings inform development of a BCL-2/BCL-xL inhibitor for NEN therapy.

Focal adhesion kinase (FAK) inhibitor APG-2449 sensitizes ovarian tumors to chemotherapy via CD44 downregulation

Abstract/Poster Number: 968
Background
Ovarian cancer is one of the deadliest malignancies in women, and up to 70% of patients with epithelial ovarian cancer have FAK overexpression, amplification, or activation. FAK plays an important role in cellular migration, growth factor signaling, cell cycle progression, cellular survival and chemoresistance. This biomarker is also significantly associated with higher tumor stage, metastasis, and shorter overall survival in patients with ovarian cancer. Inhibition of FAK is therefore emerging as a promising treatment target. APG-2449 is a clinical stage FAK/ALK/ROS1 multi-kinase inhibitor. In this study we investigated antitumor activity of APG-2449 combined with standard-of-care chemotherapeutics in ovarian cancer in the preclinical setting.

Conclusion
In summary, our data suggest that FAK inhibition by APG-2449 sensitizes ovarian tumors to chemotherapeutics in preclinical tumor models of ovarian cancer. The synergistic antitumor activity was mediated by downregulation of CD44⁺ or ALDH1⁺ cancer stem cell populations. These findings encourage clinical development of APG-2449 in combination with chemotherapies for treatment of ovarian cancer.