Puma Biotechnology Presents Clinical Data on Neratinib at the AACR Annual Meeting 2025

Puma Biotechnology, Inc. (NASDAQ:PBYI), a biopharmaceutical company, announced that clinical data on neratinib were presented in a poster session at the American Association for Cancer Research (AACR) Annual Meeting 2025. The AACR Annual Meeting is currently taking place at the McCormick Place in Chicago, Illinois. The poster is entitled, "CT071: Phase I trial of trastuzumab deruxtecan in combination with neratinib in solid tumors with HER2 alterations (NCI 10495)." Andrew A. Davis, Assistant Professor at Washington University School of Medicine, presented the poster during Session PO.CT01.01 – First-in-Human Phase I Clinical Trials 1.

NCI 10495 is sponsored by the National Cancer Institute, part of National Institutes of Health, and conducted in the NCI funded Experimental Therapeutics Clinical Trials Network (ETCTN). This open label, multi-center, Phase I clinical trial (NCT05372614) enrolled 20 patients in three cohorts treated with three increasing dose levels, or a 3+3 trial design, to evaluate the safety and tolerability of trastuzumab deruxtecan (T-DXd or ENHERTU^®) in combination with neratinib (NERLYNX^®). Eligible patients had advanced solid tumors with HER2 immunohistochemistry 3+ (IHC3+), HER2 amplification identified by in situ hybridization or next-generation sequencing, or an activating HER2 mutation. Prior treatment with trastuzumab deruxtecan was not allowed. The dose of trastuzumab deruxtecan was fixed at 5.4 mg/kg. The three dose levels (DLs) for neratinib all started at 120 mg daily for the first week. DL1 remained at 120 mg daily throughout the course of treatment, DL2 escalated to 160 mg daily in week 2 and 200 mg by week 3, and DL3 escalated to 160 mg in week 2 and 240 mg by week 3. The primary endpoints were the determination of the dose-limiting toxicities (DLTs) during the first two cycles of treatment (42 days) and the determination of the recommended Phase II dose of the combination of trastuzumab deruxtecan and neratinib.

Twenty patients received study treatment (DL1 N=7, DL2 N=4, and DL3 N=9). The most common treatment-emergent adverse events of any grade included nausea (N=15, 75%), diarrhea (N=15, 75%), fatigue (N=13, 65%), and hypokalemia (N=11, 55%). Grade 3 treatment-emergent adverse events that occurred in more than 2 patients included anemia (N=6, 30%), diarrhea (N=4, 20%), and hypokalemia (N=3, 15%). The only Grade 4 treatment-related adverse event was neutropenia that occurred in 1 patient (5%). One DLT (acute kidney injury) was observed at DL1, 0 DLTs were observed in DL2, and 1 DLT was observed (fatigue leading to early drug discontinuation) at DL3. Three patients developed Grade 1 pneumonitis or interstitial lung disease (ILD), 2 at DL1 and 1 at DL3. The proportion of reported treatment-emergent adverse events was lower at higher dose levels.

Of 15 response-evaluable patients by RECIST v1.1, 4 patients had a partial response (PR), including patients with gastroesophageal (N=2, one HER2 IHC 3+ and one HER2 mutated), pancreatic (N=1, IHC 3+), and ovarian (N=1, IHC 3+; unconfirmed response) cancers. Notably, 3 of 5 patients with advanced pancreatic cancer were observed to have tumor regression (1 PR for 13+ cycles, 2 with stable disease consisting of one patient with -29.4% tumor regression for 9 cycles and one patient with -13.3% tumor regression for 8 cycles).

Dose level 3, which consisted of trastuzumab deruxtecan at 5.4 mg/kg and neratinib at 120 mg in week 1, 160 mg week 2, and 240 mg week 3 onward, was selected as the recommended Phase II dose. Part 2 of this study, which consists of a pharmacodynamic evaluation of trastuzumab deruxtecan (5.4 mg/kg) and neratinib (RPD2) in 12 patients, opened to enrollment in March 2025. Patients with any advanced solid tumor and HER2 amplification/overexpression or a HER2 mutation will be enrolled.

"Neratinib and trastuzumab deruxtecan showed impressive combination activity in preclinical models of HER2-mutated breast cancers, which prompted evaluation of the combination in this first-in-human clinical trial. I am pleased to report that the combination not only had a manageable safety profile, but we also observed early signs of efficacy across a variety of HER2-altered tumors," said Dr. Davis.

Alan H. Auerbach, Chief Executive Officer and President of Puma Biotechnology, added, "We are pleased with the tolerability and potentially promising signals of efficacy of neratinib in combination with trastuzumab deruxtecan, especially in hard-to-treat tumors including pancreatic cancer. We look forward to continued evaluation of this combination in the Phase II portion of this study."

NCI 10495 is also supported by Puma Biotechnology and Daiichi Sankyo, Inc. through Cooperative Research and Development Agreements with NCI.

Trastuzumab deruxtecan is a specifically engineered HER2 directed DXd antibody drug conjugate (ADC) discovered by Daiichi Sankyo (TSE: 4568) and being jointly developed and commercialized by Daiichi Sankyo and AstraZeneca (NASDAQ:AZN).

About Puma Biotechnology

Puma Biotechnology, Inc. is a biopharmaceutical company with a focus on the development and commercialization of innovative products to enhance cancer care. Puma in-licensed the global development and commercialization rights to PB272 (neratinib, oral) in 2011. Neratinib, oral was approved by the U.S. Food and Drug Administration in 2017 for the extended adjuvant treatment of adult patients with early stage HER2-overexpressed/amplified breast cancer, following adjuvant trastuzumab-based therapy, and is marketed in the United States as NERLYNX® (neratinib) tablets. In February 2020, NERLYNX was also approved by the FDA in combination with capecitabine for the treatment of adult patients with advanced or metastatic HER2-positive breast cancer who have received two or more prior anti-HER2-based regimens in the metastatic setting. NERLYNX was granted marketing authorization by the European Commission in 2018 for the extended adjuvant treatment of adult patients with early stage hormone receptor-positive HER2-overexpressed/amplified breast cancer and who are less than one year from completion of prior adjuvant trastuzumab-based therapy. NERLYNX® is a registered trademark of Puma Biotechnology, Inc.

In September 2022, Puma entered into an exclusive license agreement for the development and commercialization of the anti-cancer drug alisertib, a selective, small molecule, orally administered inhibitor of aurora kinase A. Initially, Puma intends to focus the development of alisertib on the treatment of small cell lung cancer and breast cancer. In February 2024, Puma initiated ALISCA™-Lung1, a Phase II clinical trial of alisertib monotherapy for the treatment of patients with extensive-stage small cell lung cancer. In November 2024, Puma initiated ALISCA™-Breast1, a Phase II clinical trial of alisertib in combination with endocrine therapy for the treatment of patients with HER2-negative, HR-positive metastatic breast cancer.

Further information about Puma Biotechnology may be found at https://www.pumabiotechnology.com.

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Alan H. Auerbach or Mariann Ohanesian, Puma Biotechnology, Inc., +1 424 248 6500

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David Schull or Olipriya Das, Russo Partners, +1 212 845 4200

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