OBI-902 Receives Consecutive FDA Orphan Drug Designation Indication Expanded to Gastric Cancer Including Gastroesophageal Junction Adenocarcinoma

OBI-902 Receives Second Orphan Drug Designations, Strengthening Its Clinical and Commercial Potential TAIPEI, Taiwan, December 05, 2025 – OBI Pharma Inc. (4174.TWO) announced that its proprietarily developed TROP2-targeted antibody-drug conjugate (ADC), OBI-902, has received another Orphan Drug Designation (ODD) from the United States Food and Drug Administration (US FDA). The new designation covers gastric cancer (GC), including gastroesophageal junction cancer (GEJC). This follows the recent ODD granted for cholangiocarcinoma, marking the second FDA ODD designation obtained within a short period and reflecting on a continued recognition of OBI-902’s clinical development potential. The US FDA’s orphan drug designation program encourages the development of therapies for rare or high unmet medical need diseases. Once granted ODD, drug developers may benefit from incentives such as tax credits for clinical trials, exemption from certain regulatory fees, and a period of marketing exclusivity. These incentives can strengthen the commercial potential of OBI-902 and create additional opportunities for global strategic collaboration. OBI-902 is the first ADC developed using OBI’s proprietary GlycOBI® technologies for site-specific glycan conjugation. The program is currently under a Phase I/II clinical trial in the United States and Taiwan to evaluate safety, pharmacokinetics, and preliminary activity. Heidi Wang, PhD, Chief Executive Officer of OBI Pharma, stated, “The consecutive FDA orphan drug designations for OBI-902 reflect the recognition of its potential in the clinics and the value of our GlycOBI® glycan-based technologies. Both cholangiocarcinoma and gastric cancer represent areas of high unmet medical need. This designation enhances the opportunities for future international collaboration and commercialization for OBI-902.” About OBI-902 OBI-902 is a TROP2-targeted antibody-drug conjugate (ADC) that carries a potent topoisomerase I inhibitor payload to kill tumor cells and with a drug-antibody ratio (DAR) of 4. TROP2 is highly expressed in a variety of solid tumors such as breast, lung, biliary, bile duct (cholangiocarcinoma), ovarian, gastric, and many other cancer types, rendering it an ideal target for cancer therapy. OBI-902 is a novel site-specific glycan-conjugated ADC using OBI’s proprietary GlycOBI® platform, which provides improved stability and enhanced hydrophilicity. OBI-902 demonstrated remarkable antitumor efficacy, improved pharmacokinetic characteristics, and a favorable safety profile in various animal models. The IND of OBI-902 was cleared by the US FDA on April 30, 2025. Since December 2021, OBI has been granted by Biosion, Inc. an exclusive license to a TROP2 targeting antibody amino acid sequence in all jurisdictions except Mainland China, Hong Kong and Macau. Biosion holds exclusive rights to that antibody sequence in Mainland China, Hong Kong and Macau. OBI holds commercial rights to OBI-992 and OBI-902 in all jurisdictions except Mainland China, Hong Kong and Macau, while Biosion holds commercial rights to OBI-992 and OBI-902 in Mainland China, Hong Kong and Macau. About GlycOBI® OBI has developed a unique clinical stage, glycan-based site-specific ADC technology (GlycOBI®), which is in a ‘Plug and Play’ format and compatible with any antibodies, linkers, and payloads in drug-antibody ratio (DAR) up to 16. Utilizing OBI’s proprietary dual-function enzyme (EndoSymeOBI®) and linker technology (HYPrOBI®), homogenous ADCs are manufactured with an efficient and scalable process under GMP conditions. The conjugation process of GlycOBI® avoids disrupting the antibody structure and ensures the ADC has similar biophysical characteristics to the native antibody. Furthermore, OBI’s linker technology has improved conjugation efficiency of the payload, reduced aggregation propensity, which provides advantages on manufacturing ADC products. GlycOBI® conjugated ADCs have overcome the limitations of traditional ADCs and achieved better antitumor activity and stability in various in vivo animal studies. GlycOBI®, EndoSymeOBI®, and HYPrOBI® are part of the armamentarium of OBI’s Obrion™ ADC Enabling Technologies that also include ThiOBI® and GlycOBI DUO®. OBI-902 is the first ADC utilizing OBI’s Obrion™ ADC enabling technology for evaluation of safety and efficacy in Cancer, currently under Phase I/II clinical trial in the US and Taiwan. About OBI Pharma OBI is a clinical stage global oncology company that is headquartered in Taiwan and established in 2002. Its mission, together with its wholly owned subsidiary OBI Pharma USA, Inc., is to develop novel therapeutic agents for patients with high unmet medical needs. OBI’s primary focus is the development of novel ADCs, including the first-generation cysteine-based TROP2 ADC, OBI-992. Using the company’s proprietary ADC enabling technology, GlycOBI®, powered by EndoSymeOBI® and HYPrOBI®; OBI has created its next-generation novel ADC pipeline, including monospecific: OBI-902 (TROP2), OBI-904 (Nectin-4), bispecific single payload (HER2 x TROP2), and bispecific, dual payload (cMET x HER3)  ADCs. To broaden the applicability of linker technology, HYPrOBI®, OBI further developed a novel ThiOBI® platform to enable irreversible cysteine-based conjugation. Additionally, OBI’s pipeline includes the first-in-class AKR1C3-targeted small-molecule prodrug OBI-3424, which selectively releases a potent DNA-alkylating antitumor agent in the presence of the aldo-keto reductase 1C3 (AKR1C3) enzyme that is highly expressed in tumors. Additional information can be found at www.obipharma.com. GlycOBI®, EndoSymeOBI®, ThiOBI®, HYPrOBI®and GlycOBI DUO® are registered trademarks of OBI Pharma. Obrion™ are trademarks under registration. Forward-Looking Statements Statements included in this press release that are not a description of historical facts are forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Such forward-looking statements include, but are not limited to, statements about future clinical trials, results and the timing of such trials and results. Such risk factors are identified and discussed from time to time in OBI Pharma’s reports and presentations, including OBI Pharma’s filings with the Taiwan Securities and Futures Bureau.

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