GENFLEET-B - VOLUNTARY ANNOUNCEMENT

GFH375 Monotherapy Data Presented at 2026 ASCO Oral Session: World's First Dedicated Data of a RAS Inhibitor for Cholangiocarcinoma Show Preliminary Efficacy; Monotherapy Activity Observed together with Prospects for Combinational Regimens in Colorectal Cancer Treatment

GenFleet Therapeutics (Shanghai) Inc. 勁方醫藥科技(上海)股份有限公司

(A joint stock company incorporated in the People's Republic of China with limited liability) (Stock Code: 2595)

VOLUNTARY ANNOUNCEMENT GFH375 Monotherapy Data Presented at 2026 ASCO Oral Session: World's First Dedicated Data of a RAS Inhibitor for Cholangiocarcinoma Show Preliminary Efficacy; Monotherapy Activity Observed together with Prospects for Combinational Regimens in Colorectal Cancer Treatment

This announcement is made by GenFleet Therapeutics (Shanghai) Inc. (the "Company" or "GenFleet", together with its subsidiaries, the "Group") on a voluntary basis to inform the shareholders and potential investors of the Company about the latest

business updates of the Group.

The board of directors of the Company (the "Board") is pleased to announce the updated clinical data of GFH375 monotherapy treating KRAS G12D-mutant solid tumors were presented in the oral abstract session at the 2026 American Society of

Clinical Oncology (ASCO) annual meeting on June 1 local time. Preliminary efficacy was observed with GFH375 monotherapy in cholangiocarcinoma (CCA) and colorectal cancer (CRC). 20 pretreated patients with CCA harboring KRAS G12D mutation completed at least one post-treatment tumor assessment: the overall response rate (ORR)

was 40% and disease control rate (DCR) was 95% across all dose levels; the ORR reached 44.4% and DCR was 94.4% at the 600 mg QD (recommended phase II dose, RP2D) level in 18 patients. Additionally, the median progression-free survival (mPFS) was 6.2 months across all dose levels.

Among 41 patients with advanced CRC, the mPFS was 4.1 months and the median overall survival (mOS) reached 10.3 months. The preliminary efficacy data demonstrated monotherapy activity of GFH375 and its therapeutic potential in combinational regimens for CRC. A phase Ib/II trial evaluating GFH375 combined with

cetuximab for CRC and other solid tumors is ongoing in China, with relevant data expected for presentation at upcoming academic conferences.

"This is the fourth consecutive selection of GFH375's clinical data for oral presentations at top-tier global academic conferences including annual meetings of ASCO, ESMO and WCLC. GFH375 is the world's first oral KRAS G12D inhibitor

progressing into phase III study for metastatic pancreatic cancer. It has been granted with China's first two Breakthrough Therapy Designations for KRAS G12D inhibitor monotherapy, in G12D-mutant pancreatic cancer and non-small cell lung cancer respectively. We are encouraged by its therapeutic potential in diverse tumor types and

look forward to more positive results from subsequent monotherapy and combinational investigations." stated Yu Wang, M.D.,Ph.D., Chief Medical Officer of GenFleet.

Preliminary Efficacy of GFH375 in Patients with Advanced Cholangiocarcinoma or Colorectal Cancer Harboring KRAS G12D Mutation (Abstract No.: 3008)

Presented by Prof. Zhengbo Song, Zhejiang Cancer Hospital

As of data cutoff date, a total of 20 patients with KRAS G12D-mutant CCA received GFH375 treatment; 85% of them were diagnosed as stage IV at baseline, with most frequent metastases occurring in liver (70%) and lung (40%); 75% had received at least two prior lines of therapy; 85% had been previously treated with immunotherapy. The

20 patients were orally administered with GFH375 at 400 mg or 600 mg QD and all of them completed at least one post-treatment assessment: target lesion shrinkage was observed in 18 patients; 40% achieved tumor reduction by at least 30%, including one case of complete response. The mPFS was 6.2 months, and the mOS was not reached.

A total of 41 patients with KRAS G12D-mutant CRC were diagnosed as stage IV at baseline, with most frequent metastases occurring in lung (82.9%) and liver (56.1%); 95.1% had received at least two prior lines of therapy. 35 patients with CRC received treatment of GFH375 monotherapy at 400-750 mg QD and finished at least one post-

treatment assessment: 27 patients achieved stable disease or partial response; 11% achieved tumor reduction by at least 30%. The mPFS was 4.1 months, and the mOS was 10.3 months.

As of data cutoff date, GFH375 monotherapy demonstrated a manageable safety/tolerability profile in CCA and CRC patients, with a mean relative dose intensity of 98.5%. The majority of treatment-related adverse events (TRAEs) were graded 1-2, in which the patients recovered with supportive treatment; the most common TRAEs

included diarrhea, nausea, vomiting, anemia and increased AST, etc. The incidence of TRAEs was comparable to that of treatment-emergent adverse events (TEAEs) throughout treatment, and no new safety signals appeared relative to previously reported safety data of GFH375 monotherapy for other solid tumors.

About GFH375/VS-7375

GFH375 is an orally active, potent, highly selective small-molecule KRAS G12D

(ON/OFF) inhibitor designed to bind to the protein of KRAS G12D non-covalently, thereby disrupting the activation of downstream pathways and effectively inhibiting tumor cell proliferation. Preclinical studies demonstrated dose-dependent inhibition in

models bearing KRAS G12D mutation; GFH375 also demonstrated low off-target risk in kinase selectivity and safety target assays. GenFleet entered into a discovery and development collaboration with Verastem to advance three novel oncology discovery programs related to RAS/MAPK pathway-driven cancers. The collaboration provides Verastem with an exclusive option to obtain a license for each of the three compounds

in the collaboration after the successful completion of pre-determined milestones in a Phase I trial. Verastem selected GFH375/VS-7375, an oral KRAS G12D (ON/OFF) inhibitor, as its lead program from the collaboration in December 2023 and the license for GFH375 that was exercised in January 2025 is the first one from this collaboration.

The licenses would give Verastem development and commercialization rights outside of China while GenFleet would retain rights inside of China.

Forward-looking Statements

Specific information in this announcement may contain or constitute forward-looking words that are not historical facts. They can be identified by using forward-looking terminology, such as "predict", "believe", "plan", "forecast", "expect", "will", "may", "should" and other words of similar meanings. Based on the management's current

beliefs, plans, estimates and expectations of the Company's operation and market trends subject to changes beyond control, the forward-looking terminology reflects the Company's beliefs, plans, estimates and expectations of future development. Actual outcome in the future may differ significantly from forward-looking words owing to

market, policy, and R&D uncertainties, among others. Subject to the above-mentioned uncertainties, the Company makes no expressed or implied guarantee as to the accuracy, completeness or feasibility of this presentation, and you are cautioned not to solely rely on such forward-looking words. Neither the company nor any of its directors, officers,

employees, shareholders, agents, related parties, consultants or representatives will be liable to you or any other person for consequences resulting from using this presentation. Investors are advised to exercise due diligence with reference to the company's official disclosures for decision-making.

GLOSSARY OF TECHNICAL TERMS

"ASCO" American Society of Clinical Oncology

"AST" aspartate aminotransferase

"CCA" Cholangiocarcinoma

"CRC" colorectal cancer

"DCR" disease control rate

"ESMO" European Society for Medical Oncology

"KRAS" Kirsten RAS, a member of the RAS family of proteins

"MAPK" mitogen-activated protein kinase, a family of proteins involved in transmitting signals from cell surface receptors to the nucleus

"mOS" median overall survival

"mPFS" median progression-free survival

"ORR" overall response rate

"QD" quaque die

"RP2D" recommended phase II dose

"TEAEs" treatment-emergent adverse events

"TRAEs" treatment-related adverse event

"WCLC" World Conference on Lung Cancer

Cautionary Statement required by Rule 18A.05 of the Rules Governing the Listing

of Securities on The Stock Exchange of Hong Kong Limited: The Company cannot guarantee that it will be able to develop, or ultimately market GFH375 successfully. Shareholders and potential investors of the Company are advised to exercise caution when dealing in the shares of the Company.

By order of the Board GenFleet Therapeutics (Shanghai) Inc. Dr. Qiang LU Chairman and Executive Director

Hong Kong, June 2, 2026