Suzhou, China, August 4, 2026 - Alphamab Oncology (stock code: 9966 HK) today announced that Jiangsu Alphamab Biopharmaceuticals Co., Ltd. (“Alphamab”, or the “Company”), a wholly-owned subsidiary of Alphamab Oncology, entered into a licensing agreement with Pathos AI, Inc. (“Pathos”) on JSKN016, a first-in-class (FIC) TROP2/HER3 bispecific antibody-drug conjugate (ADC) independently developed by Alphamab.

Pursuant to the licensing agreement, Alphamab granted Pathos an exclusive license to research, develop, manufacture and commercialize JSKN016 in territories outside the Chinese Mainland, Hong Kong, Macau and Taiwan, with Pathos bearing all related development and commercialization costs and expenses under the agreement. Alphamab retains its full and exclusive rights to develop, manufacture and commercialize JSKN016 in the Chinese Mainland, Hong Kong, Macau and Taiwan.

Under the terms of the agreement, Alphamab is entitled to receive a non‑refundable upfront payment of US$125 million and milestone payments based on the achievement of certain development and commercialization milestones, totaling up to US$2,093 million, as well as tiered royalties at high‑single digit to low‑double digit percentage rates according to aggregate annual net sales in the licensed territories.

Alphamab also has been granted a warrant by Pathos to subscribe for shares of Pathos' preferred stock, with an aggregate subscription price of US$62.5 million (subject to adjustment in accordance with the terms of the overall transaction). Alphamab has sole discretion as to whether to exercise the warrant. If the Company elects to exercise the warrant, the relevant investment arrangements and documents will be separately executed and disclosed.

JSKN016 is a TROP2/HER3 targeting bispecific ADC independently developed by Alphamab using its proprietary single-domain antibody, bispecific antibody and glycan‑specific conjugation platforms. Through glycan‑specific conjugation, the drug achieves a homogeneous structure with a drug-to-antibody ratio (DAR) of 4, showing high stability and low off‑target toxicity. In terms of mechanism of action, on one hand, it can precisely bind to TROP2 and/or HER3 on tumor cells to block tumor signaling pathways; on the other hand, it site‑specifically releases topoisomerase I inhibitors to exert anti-tumor effects. JSKN016 has demonstrated encouraging antitumor activity and a favorable safety profile in a variety of solid tumors. Multiple Phase II clinical studies of JSKN016 as monotherapy and in combination therapies for lung cancer, breast cancer, and other indications have been initiated, and a Phase III clinical study for the treatment of triple‑negative breast cancer (TNBC) is currently ongoing.

Dr. Ting Xu, Chairman, and CEO of Alphamab Oncology, commented, "JSKN016 represents the best of our next-generation bispecific ADC platform, and we are excited to partner with Pathos. With Pathos' leading capabilities in AI-driven precision development, we are confident this collaboration will accelerate the global clinical advancement of JSKN016 and bring a potential breakthrough therapy to more patients with solid tumors. This partnership reflects our shared commitment to delivering differentiated innovation to patients worldwide."

Iker Huerga, CEO of Pathos, commented, "JSKN016 is a next-generation bispecific ADC with the potential to address significant unmet need across a range of solid tumors, and we are excited to advance it in partnership with Alphamab. This collaboration reflects our shared commitment to bringing differentiated therapies to patients."

About JSKN016

JSKN016 is a TROP2/HER3 targeting bispecific ADC developed using the proprietary single-domain antibody and bispecific antibody platforms. It is conjugated via site-specific glycosylation to generate a homogeneous and stable ADC with a drug-to-antibody ratio (DAR) of 4. JSKN016 binds to TROP2 and/or HER3 on tumor cells, blocks the corresponding signaling pathways and releases topoisomerase I inhibitors through cellular endocytosis, exerting anti-tumor effects.

JSKN016 has demonstrated superior efficacy and a favorable safety profile across multiple solid tumors. Multiple clinical studies of JSKN016 as monotherapy and in combination therapies for lung cancer, breast cancer, and other indications have been initiated. The Phase III clinical study evaluating JSKN016 for the treatment of triple-negative breast cancer (TNBC) is currently ongoing. The Phase Ib clinical study in China and the Phase I clinical study in Australia of the subcutaneous formulation of JSKN016 are both ongoing.

About Alphamab Oncology

Alphamab Oncology (Stock Code: 9966.HK) is an innovative biopharmaceutical company focused on oncology. Leveraging proprietary platforms-including single-domain antibodies, bispecific antibodies, glycan-specific conjugation, linker-payloads, dual-payload ADCs, and high-concentration subcutaneous formulations, the Company has built a differentiated and globally competitive pipeline, covering cutting-edge candidates in ADCs, bispecific antibodies, and single-domain antibodies.

Two products have received market approval: Envafolimab (KN035, brand name: 恩维达^®), the world's first subcutaneously injected PD-(L)1 inhibitor, offering greater convenience and accessibility in cancer treatment; and Anbenitamab (KN026, brand name: 恩尼妥^®), the first domestically developed HER2 bispecific antibody approved for marketing in China, redefining the standard of treatment for second‑line HER2‑positive gastric cancer. Six bispecific ADC and dual-payload ADC candidates are currently in clinical development, and next-generation ADC pipelines are advancing rapidly. The Company has established strategic partnerships with organizations including CSPC, ArriVent, Glenmark, and Pathos, covering both product development and technology platforms.

Our overarching mission is to make cancer manageable and curable by addressing unmet clinical needs in oncology. Alphamab Oncology is continuously dedicated to the development of effective, safe, and globally competitive anti-tumor drugs, enabling patients to achieve long-term, high-quality survival and delivering China-innovated cancer therapies to benefit patients worldwide.

About Pathos

Pathos is a corporation organized and existing under the laws of Delaware and a clinical-stage biotechnology company focused on precision medicine, artificial intelligence driven drug development, and the clinical development of oncology therapeutics. By combining large-scale multimodal data with proprietary AI, Pathos identifies patient populations most likely to benefit from novel therapies, informs clinical trial design, and accelerates high-confidence Go/No-Go decisions across its pipeline.

Pathos is headquartered in New York City, NY. For more information, visit www.pathos.com.

Alphamab Oncology Forward-Looking Statements

This press release contains statements related to our future business，financial performance and future events involving Alphamab Oncology that may constitute forward-looking statements. These statements include projections and estimates and relevant assumptions, statements regarding plans and expectations and statements regarding future activities, operations and performance. These statements may be identified by words such as "expect," "look forward to," "anticipate" "intend," "plan," "believe," "seek," "estimate," "will," or words of similar meaning. Such statements are based on the certain assumptions of Alphamab Oncology’s management and business operations, which are subject to various risks and uncertainties, including but not limited to political, economic, legal and business environment. The actual results, performance or achievements of Alphamab Oncology may (negatively or positively) vary materially from those described explicitly or implicitly in the relevant forward-looking statements. Unless otherwise required by applicable laws, Alphamab Oncology does not undertake obligation to publicly update any forward-looking statement nor liability for the failure to materialize such forward-looking statements, whether because of new information, future events or otherwise.

Pharmaceutical Information Statements

Alphamab Oncology does not recommend the clinical use of any already approved or under-development drugs/indications. Any information contained in this press release should not be regarded as any drug application, promotion or advertisement.