I-Mab Announces Multiple Advancements of 4-1BB Bispecific Antibody Portfolio

First patient dosed in U.S. phase 1 clinical trial of TJ-CD4B/ABL111 in patients with advanced or metastatic solid tumors

China sites to join the dose expansion part of the study to accelerate TJ-CD4B/ABL111 development

Results of TJ-L14B/ABL503 preclinical studies accepted for publication in Journal for ImmunoTherapy of Cancer

SHANGHAI and GAITHERSBURG,MD.,July 1,2021 -- I-Mab (the "Company") (Nasdaq: IMAB),a clinical-stage biopharmaceutical company committed to the discovery,development,and commercialization of novel biologics,today announced multiple advancements in its 4-1BB bispecific antibody portfolio. Stimulation of 4-1BB is a promising therapeutic strategy for improving the current immunotherapy for cancers. I-Mab's lead bi-specific antibody assets TJ-CD4B/ABL111 and TJ-L14B/ABL503,both jointly developed with ABL Bio,Inc. (Kosdaq: 298380),are undergoing clinical development in the United States.

TJ-CD4B/ABL111 is the only clinical-stage bispecific antibody that binds to Claudin 18.2 (CLDN18.2)-expressing cancer cells and co-stimulatory molecule 4-1BB on immune cells to elicit a localized and combined immune response against solid tumors. Preclinical studies have demonstrated superior CLDN18.2-dependent immune activation with TJ-CD4B/ABL111 compared to 4-1BB monoclonal antibodies. The anti-tumor activity is achieved locally at the tumor site with no hepatotoxicity or systemic side effects that are commonly seen with 4-1BB monoclonal antibodies when used alone. Studies have also demonstrated a memory response that can resist tumor rechallenge for a long-lasting treatment effect.

A U.S. phase 1 clinical trial of TJ-CD4B/ABL111 in advanced or metastatic solid tumors (NCT04900818) has been initiated with the first patient being dosed on June 29,2021. The phase 1 clinical study is a multi-center dose escalation and dose expansion study. To accelerate TJ-CD4B/ABL111 development,China sites will join the dose expansion part of the study. Patients with gastric cancer,esophageal adenocarcinoma and pancreatic cancer in China will be enrolled later this year.

TJ-L14B/ABL503 is another novel bispecific antibody uniquely designed to activate 4-1BB signalling in the presence of PD-L1,while simultaneously blocking PD-1/PD-L1 signalling. Preclinical studies have demonstrated superior anti-tumor activity for TJ-L14B/ABL503 compared to equimolar doses of 4-1BB and PD-L1 monoclonal antibodies single agents alone or in combination. The data suggest that TJ-L14B/ABL503 induced anti-tumor response was protective against tumor rechallenge in animal studies. These results have now been accepted for publication by the Journal for ImmunoTherapy of Cancer (JITC),titled "Novel anti-4-1BB X PD-L1 bispecific antibody augments anti-tumor immunity through tumor-directed T-cell activation and checkpoint blockade." A phase 1 clinical trial for TJ-L14B/ABL503 was initiated in the U.S. earlier in April 2021 in patients with locally advanced or metastatic solid tumors (NCT04762641).

"As the next-wave of innovation in immuno-oncology,bispecific antibodies could be a promising solution to cancers that are resistant to the existing standard of care," said Dr. Joan Shen,CEO of I-Mab. "With the rapid development of our bispecific antibody portfolio,we are excited to progress one of the world's first echelon of 4-1BB bispecific antibodies in the clinic."

About TJ-CD4B/ABL111

TJ-CD4B,also known as ABL111,is a Claudin 18.2 and 4-1BB bispecific antibody capable of binding to tumor cells expressing Claudin 18.2,i.e.,gastric cancer and pancreatic cancer cells,and stimulating intra-tumoral T cells by the 4-1BB arm designed to be activated only upon tumor engagement whilst silent elsewhere. TJ-CD4B effectively maintains a strong tumor binding property and anti-tumor activity attributable to a synergistic effect of both Claudin 18.2 antibody and 4-1BB antibody while it avoids or minimizes liver toxicity and systemic immunotoxicity commonly seen with 4-1BB antibodies as a drug class. TJ-CD4B is being developed under collaboration between I-Mab and ABL.

About TJ-L14B/ABL503

Being developed jointly with ABL,TJ-L14B/ABL503 is a differentiated PD-L1-based bispecific antibody with the PD-L1 arm as the tumor-dependent T-cell activator and the 4-1BB arm as the conditional T cell activator upon tumor engagement. Using ABL's 'Grabody-T' bispecific antibody platform technology,TJ-L14B/ABL503 stimulates 4-1BB activation only in the presence of PD-L1 expressing tumor cells to minimize the risk of off-tumor toxicity. Preclinical studies have demonstrated that the bispecific antibody shows better anti-tumor activity than equimolar doses of single agents alone or in combination.

About I-Mab

I-Mab (Nasdaq: IMAB) is an innovation-driven global biotech company focusing on discovery,development and soon commercialization of novel and highly differentiated biologics in immuno-oncology therapeutic area. The Company's mission is to bring transformational medicines to patients around the world through drug innovation. I-Mab's globally competitive pipeline of more than 15 clinical and pre-clinical stage drug candidates is driven by its internal R&D capability and global licensing partnerships,based on the Company's unique Fast-to-Proof-of-Concept and Fast-to-Market pipeline development strategies. The Company is now rapidly progressing from a clinical stage biotech company to a fully integrated global biopharmaceutical company with cutting-edge global R&D capabilities,a world-class GMP manufacturing facility and commercialization capability. I-Mab has established its global footprint in Shanghai (headquarters),Beijing,Hangzhou and Hong Kong in China,and Maryland and San Diego in the United States. For more information,please visithttp://ir.i-mabbiopharma.comand follow I-Mab onLinkedIn,TwitterandWeChat.

I-Mab Forward Looking Statements

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 and other federal securities laws,including statements regarding data from the TJ-CD4B/TJ-L14Bclinical trials,the potential implications of clinical data for patients,and the advancement by I-Mab and ABL,and anticipated clinical development,regulatory milestones and commercialization of TJ-CD4B/TJ-L14B.Actual results may differ materially from those indicated in the forward-looking statements as a result of various important factors,including but not limited to the ability of I-Mab and ABL to demonstrate the safety and efficacy of TJ-CD4B/TJ-L14B; the clinical results for the drug candidate,which may not support further development or NDA/BLA approval; the content and timing of decisions made by the relevant regulatory authorities regarding regulatory approval of the drug candidate; the ability to achieve commercial success for the drug candidate,if approved; I-Mab's ability to obtain and maintain protection of intellectual property for its technology and drugs; I-Mab's reliance on third parties to conduct drug development,manufacturing and other services; I-Mab's limited operating history and I-Mab's ability to obtain additional funding for operations and to complete the development and commercialization of its drug candidates; and the impact of the COVID-19 pandemic on the Company's clinical development,commercial and other operations,as well as those risks more fully discussed in the "Risk Factors" section in I-Mab's most recent annual report on Form 20-F,as well as discussions of potential risks,uncertainties,and other important factors in I-Mab's subsequent filings with the U.S. Securities and Exchange Commission. All forward-looking statements are based on information currently available to I-Mab,and I-Mab undertakes no obligation to publicly update or revise any forward-looking statements,whether as a result of new information,future events or otherwise,except as may be required by law.

For more information,please contact:

I-Mab

Jielun Zhu,Chief Financial Officer

E-mail: jielun.zhu@i-mabbiopharma.com

Office line: +86 21 6057 8000

Gigi Feng,Chief Communications Officer

E-mail: gigi.feng@i-mabbiopharma.com

Office line: +86 21 6057 5709

Investor Inquiries:

The Piacente Group,Inc.

Emilie Wu

E-mail: emilie@thepiacentegroup.com

Office line: + 86 21 6039 8363

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