Current Report by Foreign Issuer (Form 6-K)

EXPLANATORY NOTE

On December 18, 2025, NovaBridge (the "Registrant"), formerly known as I-Mab, announced its results for the nine months ended September 30, 2025 including the report and unaudited condensed consolidated financial statements included in this Form 6-K.

The information in this report on Form 6-K shall be deemed to be incorporated by reference into the Registrant's Registration Statements on Form F-3 (File No. 333-286954) and Form S-8 (File Nos. 333-239871, 333-265684, 333-256603, 333-279842, and 333-290195) and to be a part thereof from the date on which this report is filed, to the extent not superseded by documents or reports subsequently filed or furnished.

TABLE OF CONTENTS

FORWARD-LOOKING STATEMENTS

This Form 6-K contains "forward-looking statements" within the meaning of Section 27A of the Securities Act of 1933, as amended (the "Securities Act"), and Section 21E of the Securities Exchange Act of 1934, as amended ("the Exchange Act"). All statements other than statements of present and historical facts and conditions are forward-looking statements. Forward-looking statements can often be identified by words or phrases, such as "may," "will," "expect," "anticipate," "aim," "estimate," "intend," "plan," "believe," "is/are likely to," "potential," "continue" or the negative of such words or other similar expressions. Such forward-looking statements reflect our current expectations and views of future events, but are not assurances of future performance. Instead, they reflect our current beliefs, expectations and assumptions regarding the future of our business, future plans and strategies, our financial needs, our operational results and other future conditions based on information currently available to us.

Such forward-looking statements included in this Form 6-K include, but are not limited to, statements relating to:

These forward-looking statements involve various risks and uncertainties. Many important factors may adversely affect such forward-looking statements and cause actual results to differ from those in any forward-looking statement, including, without limitation, the factors described under "Risk Factors" in our Annual Report on Form 20-F for the year ended December 31, 2024 filed with the SEC on April 3, 2025 (the "Annual Report") and under "Risk Factors" in any other reports that we file with the SEC. As a result of these factors, we cannot assure you that the forward-looking statements in this report will prove to be accurate. Furthermore, if our forward-looking statements prove to be inaccurate, the inaccuracy may be material. In light of the significant uncertainties in these forward-looking statements, you should not regard these statements as a representation or warranty by us or any other person that we will achieve our objectives and plans in any specified time frame or at all. We undertake no obligation to publicly update any forward-looking statements, whether as a result of new information, future events or otherwise, except as required by law. In addition, even if

our results of operations, financial condition and liquidity are consistent with the forward-looking statements contained in this report, those results or developments may not be indicative of results or developments in subsequent periods.

MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS

Our investors should read the following discussion and analysis of our financial condition and results of operations in conjunction with our unaudited condensed consolidated financial statements and related notes for the nine months ended September 30, 2025, as well as our audited consolidated financial statements and related notes included in our Annual Report.

In this MD&A, unless otherwise indicated or the context otherwise requires, "we," "us," "our," the "Company," the "Group" and "NovaBridge" refer to NovaBridge Biosciences (formerly known as I-Mab), a Cayman Islands exempted company, and its consolidated subsidiaries, unless the context otherwise required. This MD&A includes trademarks, trade names and service marks, certain of which belong to us and others that are the property of other organizations. Solely for convenience, trademarks, trade names and service marks referred to in this MD&A appear without the ®, ™and SM symbols, but the absence of those symbols is not intended to indicate, in any way, that we will not assert our rights or that the applicable owner will not assert its rights to these trademarks, trade names and service marks to the fullest extent under applicable law. We do not intend our use or display of other parties' trademarks, trade names or service marks to imply, and such use or display should not be construed to imply, a relationship with, or endorsement or sponsorship of us by, these other parties.

Our condensed consolidated financial statements are prepared in accordance with generally accepted accounting principles in the United States, or U.S. GAAP. For the periods presented in our condensed consolidated financial statements included elsewhere in this MD&A, our reporting currency is U.S dollars. All references in this MD&A to "$" are to U.S. dollars, and all references to "RMB" are to Renminbi. Tabular amounts are in U.S. dollars in thousands, except for share and per share amounts, unless otherwise noted. This MD&A contains certain translations of RMB amounts into U.S. dollars. We make no representation that the RMB or U.S. dollar amounts referred to in this MD&A could have been or could be converted into U.S. dollars or RMB, as the case may be, at any particular rate or at all.

Overview

We are a global biotechnology platform company dedicated to bringing paradigm-shifting innovative treatments to the global markets in an accelerated and capital efficient manner. Since our inception, we have built a track record of identifying and developing novel and highly differentiated therapeutics worldwide. Our core product, givastomig, is a novel bispecific antibody ("bsAb") simultaneously targeting Claudin 18.2 ("CLDN18.2"), a tumor antigen preferentially expressed in gastric, esophageal, and pancreatic cancers, and 4-1BB, a co-stimulatory molecule on T cells.

Since the commencement of our operations in 2014, we have devoted most of our efforts and financial resources to organizing and staffing our operations, formulating business planning, raising capital, establishing our intellectual property portfolio and conducting preclinical and clinical trials of our drug candidates. On February 6, 2024, we entered into definitive agreements to divest 100% equity interest in I-Mab Biopharma Co., Ltd, our divested People's Republic of China (the "PRC") subsidiary that operated our company's business in China (the "Greater China assets and business operations"), including our rights to investigational drugs with Greater China rights that we divested, including (i) drug candidates we in-licensed from reputable global biopharmaceutical companies and (ii) drug candidates we developed or co-developed in-house (collectively, the "Greater China portfolio"), to I-Mab Biopharma (Hangzhou) Co., Ltd. (later renamed TJ Biopharma (Hangzhou) Co., Ltd. and referred to herein as "TJBio Hangzhou" or "TJ Biopharma") for an aggregate consideration of the RMB equivalent of up to $80 million, contingent on the achievement of certain future regulatory and sales-based milestone events as well as royalties. Greater China refers to the PRC, including, for the purposes of this report only, Hong Kong, Macau and Taiwan. After the completion of the divestiture on April 2, 2024, we no longer own any rights to the Greater China portfolio.

Recent Business Developments

Hong Kong Initial Public Offering

On October 31, 2025, we filed an application with the Stock Exchange of Hong Kong Limited (the "Hong Kong Stock Exchange") in connection with a proposed dual primary listing of the Company's ordinary shares, par value $0.0001 per share, on the Main Board of the Hong Kong Stock Exchange together with an initial public offering of the ordinary shares on the Hong Kong Stock Exchange.

Business Model Update

On October 16, 2025, we announced the adoption of a new business model designed to identify and advance high-value therapeutic assets through strategic partnerships and specialized subsidiary entities. Under this model, we expect to transition into a biotechnology

platform company which will establish separate subsidiaries responsible for the development of therapeutically focused assets to enhance oversight, operational focus, and risk management. On October 24, 2025, pursuant to shareholder approval at the Extraordinary General Meeting of Shareholders, we changed our name from I-Mab to NovaBridge Biosciences. As a result, our American Depositary Shares ("ADSs") trade on Nasdaq under the new name and a new ticker symbol, "NBP", effective as of October 30, 2025, replacing the former symbol "IMAB."

Visara / VIS-101

To expand our pipeline beyond oncology and into the field of ophthalmology, we have licensed-in the rights to develop, commercialize and otherwise exploit VIS-101, formerly known as AM712 or ASKG712, in all countries and territories worldwide except for Singapore, Thailand, Malaysia, Indonesia, Vietnam, the PRC, Taiwan, Macau, Hong Kong, Korea, and India (the "Visara Territory").

To facilitate the VIS-101 in-license transaction, we established Visara, Inc. ("Visara"), initially as a wholly owned subsidiary, which has subsequently become a company jointly owned by us and AffaMed Therapeutics (HK) Limited ("AffaMed") pursuant to a Series A Preferred Stock Subscription Agreement (the "Series A Agreement") entered into on October 14, 2025. Pursuant to the Series A Agreement, we subscribed for and purchased 35 million shares of Series A preferred stock of Visara for an aggregate purchase price of approximately $37 million, and AffaMed subscribed for and purchased approximately 16.2 million Series A Shares. AffaMed's subscription was made in exchange for the assignment of certain rights, title, and interest related to VIS-101. Also on October 14, 2025, Visara entered into an Assignment and Assumption Agreement with AffaMed pursuant to which AffaMed assigned, and Visara assumed, certain rights and obligations of AffaMed under the Exclusive License Agreement, dated November 6, 2021, between AffaMed and AskGene Pharma, Inc. ("AskGene"), and the Safety Data Exchange Agreement, dated August 25, 2022, between AffaMed and AskGene (such transactions, the "Assignment"). The Assignment became effective upon the closing of the transactions contemplated by the Series A Agreement and, as consideration for the Assignment, we made an upfront payment to AffaMed in the amount of $5 million.

On October 15, 2025, Visara entered into an Exclusive License Agreement (the "Exclusive License Agreement") with AskGene pursuant to which AskGene granted Visara an exclusive royalty bearing license, with the rights to sublicense under certain intellectual property rights, to develop VIS-101, currently known as ASKG712, in Singapore, Thailand, Malaysia, Indonesia, Vietnam, the PRC, Taiwan, Macau, Hong Kong, Korea, and India (the "Everest Territory"). Visara made an upfront payment to AskGene in the amount of $7 million as consideration. In addition, Visara agreed to reimburse AskGene for certain out of pocket expenses incurred in connection with the initiation of its Phase 2a study and long-term toxicology study up to an aggregate amount of RMB24 million.

On October 28, 2025, Visara entered into an Assignment and Assumption Agreement with Everest Medicines (Singapore) Pte. Ltd. ("Everest"), a subsidiary of Everest Medicines Limited, pursuant to which Visara assigned, and Everest assumed, certain rights and obligations of Visara under the Exclusive License Agreement. Everest reimbursed Visara for amounts due to AskGene prior to the assignment, including the upfront payment in the amount of $7 million. Everest Medicine Limited is an affiliate of CBC Group, and one of our existing shareholders.

Bridge Health

On October 28, 2025, our wholly owned subsidiary, I-Mab Biopharma Hong Kong Limited ("I-Mab Biopharma") announced the closing of the equity purchase agreement to acquire 100% ownership of Bridge Health Biotech Co., Ltd ("Bridge Health"). The transaction is expected to provide us with the rights to bispecific and multi-specific applications based on the CLDN18.2 parental antibody used in givastomig. Under the terms of the equity purchase agreement, we will pay Bridge Health shareholders an upfront payment of $1.8 million and non-contingent payments of $1.2 million through 2027. In addition, Bridge Health shareholders may receive future milestone payments of up to $3.875 million, subject to the achievement of certain development and regulatory milestones.

Underwritten Offering

On August 1, 2025, we entered into an underwriting agreement with Leerink Partners LLC as the representative of the several underwriters named therein, in connection with our issuance and sale in an underwritten offering (the "Offering") of 33,333,330 ADSs, each 10 ADS representing 23 ordinary shares, representing, in the aggregate, 76,666,659 ordinary shares, par value $0.0001 per share, of the Company at an offering price of $1.95 per ADS. Net proceeds from the Offering, after deducting underwriting discounts and commissions and offering expenses payable by us, were approximately $61.2 million.

Key Factors Affecting Our Results of Operations

Our results of operations, financial condition, and the period-to-period comparability of our financial results have been, and are expected to continue to be, principally affected by the below factors:

Research and Development Expenses

Our results of operations are significantly affected by our cost structure, which primarily consists of research and development expenses and administrative expenses.

Research and development activities are central to our business model. We believe our ability to successfully develop drug candidates is the primary factor affecting our long-term competitiveness, as well as our future growth and development. Developing high-quality drug candidates requires a significant investment of resources over a prolonged period of time, and a core part of our strategy is to continue making sustained investments in this area. Since our inception, we have focused our resources on our research and development activities, including conducting preclinical studies and clinical trials, and activities related to regulatory filings for our drug candidates. Our research and development expenses primarily include the following:

Our research and development costs may increase period over period as we continue to support and advance the clinical trials of our drug candidates.

Administrative Expenses

Our administrative expenses consist primarily of employee salaries and related benefit costs. Other administrative expenses include service fees for legal, intellectual property, consulting and auditing services as well as other direct and allocated expenses such as rent on our facilities, travel costs and other supplies used in administrative activities.

Revenue from Out-Licensing Agreements

We continue to seek out-licensing opportunities for our drug candidates through our network of global partnerships and alliances. As we have not obtained marketing approval for a commercialized drug candidate, our historical revenues were primarily subject to the availability of payments from granting licenses to research, develop and otherwise exploit certain of our drug candidates, and supply of the investigational products thereof. For the nine months ended September 30, 2025 and 2024, we did not generate any revenue.

In addition, after validating clinical safety and preliminary efficacy of a drug candidate in our Global portfolio in clinical trials in the United States, we may elect to out-license certain rights of such drug candidate, but we may choose to retain these rights for the United States or other countries or regions as we may deem fit. Global portfolio refers to our own in-house developed or co-developed novel or differentiated drug candidates, for most of which we own worldwide, ex-Greater China rights. Before the commercialization of one or more of our drug candidates, we expect that the majority of our revenue will be generated from out-licensing our intellectual properties.

Funding for Our Operations

Historically, we have funded our operations primarily through public and private placements, as well as revenue from licensing and collaboration deals. In the future, in the event of successful commercialization of one or more of our drug candidates, we expect to fund our operations in part with revenue generated from sales of our commercialized drug products. However, we believe we will need to raise additional capital to complete the development and commercialization of our other drug candidates. Such funding may take the form of public or private offerings, debt financing, collaborations, licensing arrangements or other sources.

Our Ability to Commercialize Our Drug Candidates

Our business and results of operations depend on our ability to commercialize our drug candidates, once and if those candidates are approved for marketing by the applicable health authority. Our pipeline consists of four clinical stage drug candidates. Although we currently do not have any product approved for commercial sale and have not generated any revenue from product sales, we expect to generate revenue from sales of our drug candidates after we complete clinical development of, obtain regulatory approval for, and successfully commercialize such drug candidates, if ever.

Our Divestiture of the Greater China Assets and Business Operations

On February 6, 2024, we entered into definitive agreements to divest our Greater China assets and business operations, including our rights to the Greater China portfolio, to TJBio Hangzhou for an aggregate consideration of the RMB equivalent of up to $80 million, contingent on the achievement of certain future regulatory and sales-based milestone events as well as royalties. After the completion of the divestiture on April 2, 2024, we do not own any rights to the Greater China portfolio, including the Greater China rights for givastomig, uliledlimab and lemzoparlimab. We no longer bear future development costs of our Greater China assets and business operations.

As a result of our divestiture of our Greater China assets and business operations, we have ceased to consolidate the divested entity, assets and businesses as well as its corresponding financial results from the second quarter of 2024 onwards.

Key Components of Results of Operations

The following results of operations relate to continuing operations.

Revenues

We did not generate any revenue for the nine months ended September 30, 2025 and 2024.

Research and Development Expenses

Research and development expenses primarily consist of: (i) payroll and other related expenses, including share-based compensation, of personnel engaged in research and development activities, (ii) fees associated with the exclusive development rights of our in-licensed drug candidates, (iii) fees for services provided by contract research organizations ("CROs"), investigators and clinical trial sites that conduct our clinical studies, and (iv) expenses relating to the development of our drug candidates, including raw materials and supplies, product testing, depreciation, and facility related expenses, and (v) other research and development expenses.

Following the completion of the divestiture of our Greater China assets and business operations on April 2, 2024, our current research and development activities primarily relate to the clinical development of the following investigational drugs:

We incurred research and development expenses of $7.2 million and $15.7 million for the nine months ended September 30, 2025 and 2024, respectively. Our research and development costs may increase period over period as we continue to support and advance the clinical trials of our drug candidates, including a global randomized Phase 2 study and additional Phase 1b cohorts for our lead program, givastomig.

Administrative Expense

Administrative expenses primarily consist of salaries and related benefit costs, including share-based compensation, for employees engaged in managerial and administrative positions or involved in general corporate functions, professional fees for consulting and auditing as well as other direct and allocated expenses such as rent on our facilities, travel costs and other supplies used in administrative activities. For the nine months ended September 30, 2025 and 2024, our administrative expenses amounted to $14.1 million and $22.3 million, respectively.

Interest Income

Interest income consists primarily of interest income derived from our money market funds and term deposits.

Other Income (Expenses), Net

Other income (expenses), net consists primarily of the settlement of TJ Biopharma repurchase obligations, fair value changes and extinguishment of put right liabilities, net realized foreign exchange gains (losses), asset impairment loss, incentive payments from our ADS depository bank, rent expenses and sublease income.

Equity In Loss of Affiliates

Equity in loss of affiliates consists primarily of the loss recognized based on our proportionate ownership in TJBio Hangzhou, our unconsolidated investee prior to the equity transfer of our interests in TJBio Hangzhou to certain participating shareholders of TJBio Hangzhou.

Results of Operations

The following table sets forth a summary of our condensed consolidated results of operations for the periods indicated. This information should be read together with our condensed consolidated financial statements and related notes. The operating results in any period are not necessarily indicative of the results that may be expected for any future period.

Nine Months Ended September 30, 2025 Compared to Nine Months Ended September 30, 2024 for Continuing Operations

Research and Development Expenses

The following table sets forth a breakdown of the major components of our research and development expenses in nominal amounts and as a percentage of our total research and development expenses for the periods indicated:

Our research and development expenses decreased by $8.5 million, or 54.0%, from $15.7 million for the nine months ended September 30, 2024 to $7.2 million for the nine months ended September 30, 2025, primarily due to reimbursements recognized under an existing collaboration agreement and lower employee benefit and compensation expenses resulting from a lower headcount.

Administrative Expenses

Our administrative expenses decreased by $8.2 million, or 36.7%, from $22.3 million for the nine months ended September 30, 2024 to $14.1 million for the nine months ended September 30, 2025, primarily due to a decrease in legal expenses and lower employee benefit and compensation expenses resulting from a lower headcount. This decrease was partially offset by higher professional service expenses and employee share-based compensation expense in the current period. The employee share-based compensation expense during the nine months ended September 30, 2024 included forfeitures in connection with the divestiture of our Greater China assets and business operations.

Interest Income

We recorded interest income of $5.8 million and $5.3 million for the nine months ended September 30, 2025 and 2024, respectively.

Other Income (Expenses), Net

We recorded other income of $0.1 million and other expense of $(5.0) million for the nine months ended September 30, 2025 and 2024, respectively. The change was primarily attributable to the settlement of repurchase obligations associated with TJ Biopharma redemptions in the prior period and smaller impacts from foreign exchange losses recognized in 2025, partially offset by changes in fair value and extinguishment of put right liabilities.

Equity in Loss of Affiliates

We recorded equity in loss of affiliates of $1.0 million for the nine months ended September 30, 2024 due to recognition of the employee stock ownership plan expenses from our unconsolidated investee as a result of the divestiture of the Greater China assets and business operations. There was no equity in loss of affiliates for nine months ended September 30, 2025.

Critical Accounting Policies and Significant Judgments and Estimates

Our reported results are impacted by the application of certain accounting policies that require us to make subjective or complex judgments. These judgments involve estimations of the effect of matters that are inherently uncertain and may significantly impact our quarterly or annual results of operations or financial condition. Changes in the estimates and judgments could significantly affect our results of operations, financial condition and cash flows in future years. A description of what we consider to be our most significant critical accounting policies and estimates is included in "Item 5. Operating and Financial Review and Prospects- A.Operating Results-Critical Accounting Policies and Significant Judgments and Estimates" in our Annual Report.

Recent Accounting Pronouncements

A list of recently issued accounting pronouncements that are relevant to us is included in Note 2 - Principal accounting policies- Recent Accounting Pronouncementsof our condensed consolidated financial statements.

Cash Flows and Working Capital

We incurred net losses and negative cash flows from our operations during the nine months ended September 30, 2025 and 2024. Substantially all of our losses have resulted from funding our research and development programs and administrative costs associated with our operations. We incurred net losses from continuing operations of $15.5 million and $38.9 million for the nine months ended September 30, 2025 and 2024, respectively. Our primary use of cash is to fund our research and development activities. We used $6.0 million and $41.7 million in cash for our operating activities for the nine months ended September 30, 2025 and 2024, respectively. As of September 30, 2025, we had cash and cash equivalents of $228.1 million and short-term investments of $0.2 million. Our cash and cash equivalents consist primarily of cash held in banks and securities with maturities of three months or less. Historically, we have financed our operations primarily through public and private placements, as well as revenue from licensing and collaboration deals. We will need to raise additional capital through various potential sources, such as equity and/or debt financings, strategic relationships, potential strategic transactions or out-licensing of our products.

The following table sets forth a summary of our cash flows for the periods presented:

We do not expect to generate any revenue from the sales of our products unless and until we obtain regulatory approval of and commercialize one of our current or future drug candidates. We anticipate that we will continue to generate losses for the foreseeable future, and we expect the losses to increase as we continue the development of, and seek regulatory approvals for, our drug candidates and begin to commercialize any approved products. In addition, subject to obtaining regulatory approval of any of our drug candidates, we expect to incur significant commercialization expenses for product sales, marketing and manufacturing. Accordingly, we will need substantial additional funding in connection with our continuing operations.

Based on our current operating plan, we believe that our current cash, cash equivalents and short-term investments of $228.3 million will be sufficient to meet our current and anticipated working capital requirements and capital expenditures for at least the next 12 months. We have based our estimates on assumptions that may prove to be wrong, and we may use our available capital resources sooner than we currently expect. Because of the numerous risks and uncertainties associated with the development and commercialization of our drug candidates, we are unable to estimate the amounts of increased capital outlays and operating expenditures necessary to complete the development and commercialization of our drug candidates.

We may decide to enhance our liquidity position or increase our cash reserve for future operations and investments through additional financing. The issuance and sale of additional equity would result in further dilution to our shareholders and ADS holders, and the terms of these securities may include liquidation or other preferences that adversely affect our investors' rights as ADS holders. The incurrence of indebtedness would result in increased fixed or variable obligations and could result in operating covenants that would restrict our operations, which could potentially dilute the interests of our shareholders. If we raise additional funds through collaborations, strategic alliances or licensing arrangements with third parties, we may have to relinquish valuable rights to our technologies, future revenue streams or research programs or to grant licenses on terms that may not be favorable to us. If we are unable to raise additional funds through equity or debt financings when needed, we may be required to delay, limit, reduce or terminate our product development or future commercialization efforts or grant rights to develop and market products or drug candidates that we would otherwise prefer to develop and market ourselves.

Operating Activities

Net cash used in operating activities the nine months ended September 30, 2025 was $6.0 million. Our net loss was $15.5 million for the same period. The difference between our net loss and our net cash used in operating activities was primarily attributable to non-cash benefits associated with share-based compensation of $2.0 million and timing impacts related to accrued expenses and other payables of $7.4 million.

Net cash used in operating activities from continuing operations for the nine months ended September 30, 2024 was $41.7 million. Our net loss was $38.9 million for the same period. The difference between our net loss and our net cash used in operating activities was primarily attributable to certain non-cash benefits, including the change in fair value and extinguishment of put right liabilities of $13.9 million, timing impacts related to prepayments and other receivables of $4.3 million and share-based compensation benefit of $2.8 million due to forfeitures in connection with the divestiture of our Greater China assets and business operations. These adjustments were partially offset by the settlement of TJ Biopharma repurchase obligations expense of $12.4 million, timing impacts associated with accruals and other payables of $3.1 million, impairments of fixed assets of $1.2 million and an equity loss in affiliates of $1.0 million.

Investing Activities

Net cash generated from investing activities for the nine months ended September 30, 2025 was $105.0 million. The net cash increase was primarily attributable to proceeds of $154.9 million from the sale of short-term investments, partially offset by purchases of $50.0 million of short-term investments.

Net cash used in investing activities from continuing operations for the nine months ended September 30, 2024 was $135.9 million. The net cash decrease was primarily attributable to $113.3 million of cash used in the purchase of short-term and other investments and $51.1 million of cash used in the purchase of available-for-sale debt securities, partially offset by proceeds from disposal of short-term and other investments of $28.5 million.

Financing Activities

Net cash generated from financing activities for the nine months ended September 30, 2025 was $60.7 million. The increase is attributable to the proceeds received from the underwritten offering of our ADS shares in the third quarter of 2025, net of deferred financing costs.

Net cash used in financing activities from continuing operations for the nine months ended September 30, 2024 was $0.3 million, which was related to stock repurchases.

Material Cash Requirements

Contractual Obligation

Our material cash requirements as of September 30, 2025 primarily include our operating lease obligations. Our operating lease commitments range from approximately 3 to 6 years lease terms, with a total commitment amount of $3.7 million as of September 30, 2025.

Other than those disclosed above, we did not have any significant capital and other commitments, long-term obligations or guarantees as of September 30, 2025.

We have entered into certain unconditional purchase obligations and other commitments in the normal course of business. There have been no changes to these commitments that would have a material impact on our ability to meet either short-term or long-term future cash requirements.

Collaborations, Licensing and Other Arrangements

We have entered into collaborative, licensing, and other arrangements with third parties that may require future milestone payments to third parties contingent upon the achievement of certain development, regulatory, or commercial milestones. Individually, these arrangements are insignificant in any one annual reporting period. However, if milestones for multiple products covered by these arrangements would happen to be reached in the same reporting period, the aggregate charge to expense could be material to the results of operations in that period. From a business perspective, the payments are viewed as positive because they signify that the product is successfully moving through development and is now generating or is more likely to generate future cash flows from product sales. It is not possible to predict with reasonable certainty whether these milestones will be achieved or the timing for achievement. See Note 12 - Licensing and collaboration arrangementsof our condensed consolidated financial statements in this filing for additional information on these collaboration arrangements.

Holding Company Structure

We are a holding company with no material operations of its own. Following the divestiture of our Greater China assets and business operations, we currently conduct our operations primarily through our subsidiary in the United States and only a small portion of business operations in China through our PRC subsidiary. As a result, our ability to pay dividends depends upon dividends paid by our U.S. and PRC subsidiaries. In the event that we may rely on dividends paid by our PRC subsidiary, there are certain limitations imposed by debt instruments or PRC laws, rules and regulations.

NovaBridge Biosciences

INDEX TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

F-1

NovaBridge Biosciences

Condensed Consolidated Balance Sheets

As of September 30, 2025 and December 31, 2024

(All amounts in thousands, except for share data, unless otherwise noted)

The accompanying notes are an integral part of these condensed consolidated financial statements.

F-2

NovaBridge Biosciences

Condensed Consolidated Statements of Comprehensive Loss

For the Nine Months Ended September 30, 2025 and 2024

(Unaudited)

(All amounts in thousands, except for share and per share data, unless otherwise noted)

The accompanying notes are an integral part of these condensed consolidated financial statements.

F-3

NovaBridge Biosciences

Condensed Consolidated Statements of Changes in Shareholders' Equity

For the Nine Months Ended September 30, 2025 and 2024

(Unaudited)

(All amounts in thousands, except for share data, unless otherwise noted)

The accompanying notes are an integral part of these condensed consolidated financial statements.

F-4

NovaBridge Biosciences

Condensed Consolidated Statements of Cash Flows

For the Nine Months Ended September 30, 2025 and 2024

(Unaudited)

(All amounts in thousands, unless otherwise noted)

The accompanying notes are an integral part of these condensed consolidated financial statements.

F-5

NovaBridge Biosciences

NOTES TO THE CONDENSED CONSOLIDATED FINANCIAL STATEMENTS

(Unaudited)

(All amounts in thousands, except for share and per share data, unless otherwise noted)

F-6

F-7

F-8

F-9

F-10

be acted without the consent from the Investor Directors. In accordance with ASC 810-10, TJBio Hangzhou was a variable interest entity, and no shareholder shall consolidate TJBio Hangzhou under VIE model as neither party had the power to direct all the activities that most significantly impact the economic performance of TJBio Hangzhou. Therefore, the Group deconsolidated TJBio Hangzhou and retained significant influence in TJBio Hangzhou. The investment was accounted for using the equity method. The retained investment in the common stock of TJBio Hangzhou was initially measured at fair value in accordance with ASC 810-10-40.

Subsequently, pursuant to TJBio Hangzhou's articles of association, the Group applied the HLBV method to allocate earnings or losses of TJBio Hangzhou because the liquidation rights and priorities sufficiently differ from what is reflected by the underlying percentage ownership interests. During the year of 2023, the Group discontinued applying the equity method since the carrying amount of the investment had been reduced to zero, and therefore, did not recognize any earnings or losses of TJBio Hangzhou after 2023.

The purchase price of $3million committed by Management Holdco under Series A SPA, representing 10% of the equity of TJBio Hangzhou, was significantly lower than the fair value of the corresponding subscribed shares as of the Closing Date. The excess was considered as share-based compensation to TJBio Hangzhou's management for the services to be used or consumed in TJBio Hangzhou's own operations. The share-based compensation was considered granted upon the Closing Date and cliff vests after five years of service from the Series A Closing Date. Consequently, the Group recognized its proportionate share of the compensation expense recorded by TJBio Hangzhou.

Along with the equity transfer transaction, the team of designated management/workforce transferred from the Group to TJBio Hangzhou consists of several grantees under the Group's 2020 Share Incentive Plan (the "2020 Plan") and 2021 Share Incentive Plan (the "2021 Plan"). These individuals continued to meet the definition of eligible participants under such plans after their resignation date from the Group. Meanwhile, there has been no change to any of the award terms. The equity transfer transaction did not trigger the modification accounting to the share-based compensation. Additionally, given that TJBio Hangzhou became an affiliate to the Group upon deconsolidation, and that the other shareholders of TJBio Hangzhou are not providing proportionate value to sponsor the 2020 Plan and 2021 Plan nor is the Group receiving any consideration for the awards granted to employees of TJBio Hangzhou, the Group is required, under Topic 323, to expense the full costs of share-based compensation as incurred in the same period as the costs are recognized by TJBio Hangzhou.

In 2024, TJBio Hangzhou granted stock options to its employees. Pursuant to TJBio Hangzhou's articles of association, the Group applied the HLBV method to allocate earnings or losses of TJBio Hangzhou because the liquidation rights and priorities sufficiently differ from what is reflected by the underlying percentage ownership interests.

Series B Investments

In July 2022, TJBio Hangzhou entered into an equity transfer and investment agreement and a shareholders agreement (the "Series B SHA") with a group of domestic investors ("Series B Domestic Investors") in China to raise approximately $46million in RMB equivalent. Once all the shares of TJBio Hangzhou are purchased by or issued to its investors, including Management Holdco and ESOP Holdco, the Group would hold 40.36% equity interest in TJBio Hangzhou. Pursuant to the Series B SHA, Management Holdco and ESOP Holdco no longer had irrevocably consented to act in concert with I-Mab Hong Kong. TJBio Hangzhou remains the affiliate of the Group. The Series B financing in TJBio Hangzhou was consummated in 2023.

Series C Investment, Equity Transfer and Shares Repurchase Transactions

On February 6, 2024, the Group entered into definitive agreements with TJBio Hangzhou and its investors to transfer the equity interests it holds in TJBio Hangzhou to certain participating shareholders of TJBio Hangzhou in exchange for the extinguishment of the existing repurchase obligations (see "-Put Right Liabilities" below) owed by I-Mab Hong Kong to those shareholders in the amount of approximately $183million. Upon the closing of the transaction on April 2, 2024, the total amount of potential repurchase obligations owed by the Group to the non-participating shareholders of TJBio Hangzhou was expected to range from $30million to $35million, an amount that included claims in legal arbitration proceedings by certain non-participating shareholders against I-Mab Hong Kong in connection with the divestiture of the Greater China assets and business operations transaction. Subsequently, during the second and

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third quarters of 2024, the Group entered into share repurchase agreements with the non-participating shareholders and repurchased TJBio Hangzhou's equity interests held by those shareholders for a price based on the investment cost plus a contractual amount of interest. As a result, the corresponding redemption obligations (see "-Put Right Liabilities" below) were fully extinguished. Concurrently with the equity transfer transaction on February 6, 2024, the Group participated in the Series C fundraising of TJBio Hangzhou and invested $19.0million in exchange for 5.65%of TJBio Hangzhou's total share capital. Upon the completion of the repurchase transactions and the Series C investment, the Group's total ownership in TJBio Hangzhou was approximately 15% as of December 31, 2024. Following TJBio Hangzhou's completion of the Series C-2 financing round on September 24, 2025, the Group's total ownership in TJBio Hangzhou decreased to approximately 12.2%as of September 30, 2025. The Group does not have the ability to exercise significant influence over the operating and/or financial policies of TJBio Hangzhou given there is no representation on the Board of Directors or shared management personnel, no participation in TJBio Hangzhou's policy-making processes, or any significant or material intra-entity transactions.

Upon the completion of the TJBio Shanghai Equity Transfer on April 2, 2025 (see Note 4 - Disposal of TJBio Shanghai for more details), TJBio Hangzhou is referred to as TJ Biopharma thereafter.

Pursuant to the Series C shareholder agreement, if TJ Biopharma fails to complete an initial public offering ("IPO") of its shares before December 31, 2027, or TJ Biopharma voluntarily withdraws the application for the IPO or the relevant regulatory authorities rejects or disapproves the application for the IPO prior to June 30, 2027, the Series A, B, and C investors will have the right to require TJ Biopharma to repurchase all or part of its investor's equity interests in cash. The Group's investment in TJ Biopharma's preferred shares are therefore contingently redeemable as TJ Biopharma's redemption obligation is only satisfied upon a future liquidity event by a specified date, which is not within the control of the investor or the issuer. As such, the Group accounted for the investment in TJ Biopharma as available-for-sale debt securities in accordance with ASC 320,Investment - Debt Securities. The investments are reported at fair value as of the transaction date and re-measured at each reporting period, with the changes in unrealized gains and losses included as a component of the accumulated other comprehensive income (loss). Any impairment of the investment due to credit-related losses is reported in the consolidated statements of comprehensive loss.

During the nine months ended September 30, 2024, the Group recognized $12.4million of expenses related to the settlement of TJ Biopharma repurchase obligations from the non-participating shareholders as the transaction price was determined based on the non-participating shareholders' initial investment cost plus a contractual amount of interest compared to the fair value of the investment that was determined by management, using a third-party valuation specialist. The estimated equity value of TJ Biopharma was established using a backsolve method based on the Series C financing transaction of TJ Biopharma. The value was subsequently adjusted as of each reporting period by applying a change in the movement of a selected set of comparable companies, biotech indices and company-specific factors, as applicable. This value was then allocated towards TJ Biopharma's Series A, B, and C capital structure using an option pricing method, or "OPM", and a waterfall approach based on the order of liquidation preferences of the Series A, B, and C shares relative to one another. In the third quarter of 2025, following TJ Biopharma's completion of the Series C-2 financing round, the equity value of TJ Biopharma as of September 30, 2025 was determined using a backsolve method based on the Series C-2 transaction share price. The resulting value was then allocated to the Series A, B, and C capital structure using the same OPM and liquidation waterfall methodology described above.

A summary of the fair value estimates of the Group's investments in available-for-sale debt securities is provided in the "-Fair Value Measurements" section below.

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In addition, various objective and subjective factors were considered to determine the fair value of the Group's Series A, B, and C shares as of each reporting period, including, among other factors:

The assumptions underlying this valuation represented management's best estimate, which involved inherent uncertainties and the application of management's judgment. This valuation is therefore sensitive to changes in the unobservable inputs. As a result, if the Group had used different assumptions or estimates, or if there are changes to the unobservable inputs, the fair value of the Series A, B and C shares could have been materially different. A summary of the unrealized gains and losses recognized in accumulated other comprehensive income (loss) related to the non-credit-related changes in the estimated fair value of the Group's investments in available-for-sale debt securities is provided in the "-Fair Value Measurements" section below.

Put right liabilities

Pursuant to the Series A SHA and Series B SHA, if TJ Biopharma failed to consummate a public offering of TJ Biopharma's shares on the China Stock Exchange's Science and Technology Innovation Board, Main Board, Small and Medium-Sized Enterprise Board, Growth Enterprise Board, or Hong Kong Stock Exchange, U.S. Stock Exchange, or other stock exchanges approved by the shareholders of TJ Biopharma in accordance with provisions of the Series A SHA and Series B SHA within four years after September 15, 2020 (the "Repurchase Scenario"), the Series A Domestic Investors and Series B Domestic Investors (collectively, the "Domestic Investors") had the right to elect to request I-Mab Hong Kong to repurchase all or any part of the equity of TJ Biopharma held by such Domestic Investors within three years of the occurrence of the Repurchase Scenario. I-Mab Hong Kong is obligated to repurchase the equity held by the Domestic Investors in cash or in NovaBridge's stock (subject to the approval procedures of NovaBridge) within one year from the date on which any of the Domestic Investors delivers request of repurchase in writing. The repurchase price is determined based on the investment cost of the Domestic Investors plus a contractual amount of interest.

The redemption obligation written by I-Mab Hong Kong to the Domestic Investors is a freestanding equity-linked instrument, which is classified as a put right liability and is initially measured at fair value. Subsequent changes in fair value are recorded in other income (expenses) in the consolidated statements of comprehensive loss.

The estimated fair value of the put right liability was determined by reducing the expected redemption obligation value by the estimated fair value of the underlying preferred shares. The fair value of the preferred shares was estimated using a backsolve method based on TJ Biopharma's Series C financing. This value was then allocated towards TJ Biopharma's Series A, B and C capital structure using an OPM, and a waterfall approach based on the order of liquidation preferences of the Series A, B, and C shares relative to one another. The resulting amount was then discounted to present value. The discount factor was derived from the average yield of a set of comparable bond yields with a weighted-average time to maturity approximating the Group's expected term to redemption, adjusted for company-specific factors and a credit rating reflective of the highly speculative nature of the investment.

The redemption obligations were fully extinguished in 2024 through equity transfer and shares repurchase transactions during the year as described under "-Investments in TJ Biopharma"above.

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Service-based Options

For the nine months ended September 30, 2025 and 2024, the Group recognized a total share-based compensation expense of $0.9millionand $(1.8) million, respectively, related to awards with service-based vesting conditions (the "Service-based Options"). The expense reduction for the nine months ended September 30, 2024 was largely driven by a significant reduction in headcount due to the shift in business strategy in 2024. As of September 30, 2025, unamortized share-based compensation expense related to unvested Service-based Options was $1.3million, which is expected to be recognized over a weighted-average period of 0.7years.

The total intrinsic value of Service-based Options exercised during the nine months ended September 30, 2025 was $0.3million. NoService-based Options were exercised during the nine months ended September 30, 2024.

During the nine months ended September 30, 2025, the Group estimated the fair value of Service-based Options using the Black Scholes Option Pricing Model ("BSOPM") on the grant dates. During the nine months ended September 30, 2024, the Group estimated the fair value of Service-based Options using the BSOPM and Binomial Option Pricing Model ("BOPM") on the grant dates. The weighted average grant-date fair value per ordinary share of Service-based Options granted during the nine months ended September 30, 2025 and 2024 was $0.55and $0.49, respectively.

The BSOPM and BOPM require a number of assumptions in order to derive a fair value determination for each type of award. Expected volatility is derived from a combination of the historical volatilities of the Group and select publicly traded peers for a period consistent with the underlying instrument's expected term. The expected term of options granted is based on historical experience and represents the period of time that options granted are expected to be outstanding. The risk-free interest rate is based on the yield curve of a zero-coupon, U.S. Treasury bond on the date the stock option award was granted with a maturity equal to the expected term of the stock option award. Dividend yields are based on the Group's history and expected future actions. The Group has historically not paid dividends and has noforeseeable plans to pay dividends.