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SIDE LETTER AGREEMENT

Side Letter to the Series Seed Preferred Stock Purchase Agreement dated February 9, 2026

February 9, 2026

This Side Letter Agreement (this "Side Letter") is entered into as of February 9, 2026, by and between:

MERIDIAN DIAGNOSTICS, INC., a Delaware corporation (the "Company"), with its principal office located at 225 Binney Street, Suite 400, Cambridge, MA 02142;

and

COBALT VENTURES FUND III, LP, a Delaware limited partnership (the "Investor"), acting through its general partner, Cobalt Ventures GP III, LLC, a Delaware limited liability company, with its principal office located at 2400 Sand Hill Road, Suite 310, Menlo Park, CA 94025.

The Company and the Investor are each referred to herein individually as a "Party" and collectively as the "Parties."

RECITALS

WHEREAS, the Company and the Investor are parties to that certain Series Seed Preferred Stock Purchase Agreement, dated as of February 9, 2026 (the "Purchase Agreement"), pursuant to which the Investor is purchasing 2,687,989 shares of Series Seed Preferred Stock of the Company at a price per share of $2.6786, for aggregate consideration of Seven Million Two Hundred Thousand Dollars ($7,200,000), as part of an aggregate financing round of Twelve Million Dollars ($12,000,000) (the "Financing");

WHEREAS, the Company and the Investor are also parties to that certain Investors' Rights Agreement dated as of the date hereof (the "IRA"), that certain Voting Agreement dated as of the date hereof (the "Voting Agreement"), and that certain Right of First Refusal and Co-Sale Agreement dated as of the date hereof (the "ROFR Agreement," and together with the Purchase Agreement, the IRA, the Voting Agreement, and this Side Letter, the "Transaction Documents");

WHEREAS, as a condition to the Investor's obligations under the Purchase Agreement, the Company has agreed to provide the Investor with certain additional rights and protections as set forth herein;

WHEREAS, the Investor is the lead investor in the Financing, committing $7,200,000 (representing 60.0% of the aggregate round size), and such additional rights reflect the Investor's significant capital commitment and leadership role in the transaction; and

NOW, THEREFORE, in consideration of the mutual promises and covenants contained herein and the Investor's purchase of shares under the Purchase Agreement, and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the Parties agree as follows:

1. DEFINITIONS

1.1 Generally. Capitalized terms used but not otherwise defined in this Side Letter shall have the meanings ascribed to such terms in the Purchase Agreement or, if not defined therein, in the IRA.

1.2 Defined Terms. As used in this Side Letter, the following terms shall have the following meanings:

(a) "Board" means the Board of Directors of the Company, as constituted from time to time in accordance with the Company's Amended and Restated Certificate of Incorporation and the Voting Agreement.

(b) "Investor Designee" means any individual designated by the Investor to serve as a board observer pursuant to Section 3 of this Side Letter.

(d) "Major Investor" has the meaning set forth in the IRA, which, as of the date hereof, means any holder of at least 1,000,000 shares of Series Seed Preferred Stock (or Common Stock issued upon conversion thereof), as adjusted for any stock splits, stock dividends, combinations, recapitalizations, or similar events.

(e) "Observer" has the meaning set forth in Section 3 below.

(f) "Qualified Financing" has the meaning set forth in the Purchase Agreement and the IRA, as applicable.

2. ADDITIONAL INFORMATION RIGHTS

2(a) Monthly KPI Dashboard.

In addition to the information rights granted to Major Investors under Section 3.1 of the IRA (which include, among other things, annual audited financial statements, quarterly unaudited financial statements, monthly management reports, and an annual budget and business plan), the Company shall prepare and deliver to the Investor a monthly key performance indicator dashboard (the "KPI Dashboard") within fifteen (15) days following the end of each calendar month. The KPI Dashboard shall include, at a minimum, the following categories of information:

(i) Cash and Burn. The Company's cash balance as of the end of such calendar month and the Company's monthly cash burn rate for such calendar month (for reference, as of the date hereof the Company's approximate monthly burn rate is $185,000);

(ii) Revenue. Revenue recognized during such calendar month, if any, and year-to-date revenue, together with a brief narrative of material revenue developments;

(iii) Headcount. Total headcount as of the end of such calendar month, broken down by department or functional area, including identification of any new hires or departures (for reference, as of the date hereof the Company employs 18 full-time employees);

(iv) Product Development. Progress updates on product development milestones for the MeridianPulse platform, including the Company's 14-marker point-of-care blood panel with a target sub-8-minute turnaround time, as well as any material changes to the product roadmap or timeline;

(v) Clinical and Regulatory. Clinical trial status updates and regulatory submissions, approvals, or material communications with the U.S. Food and Drug Administration or other applicable regulatory authorities;

(vi) Pipeline Metrics. Key customer acquisition and partnership pipeline metrics, including the number of active prospective customer or partner discussions, any executed letters of intent or term sheets, and material changes to existing commercial relationships; and

(vii) Other Metrics. Such other metrics or information as the Investor may reasonably request from time to time upon not less than ten (10) business days' prior written notice to the Company, provided that the Company shall not be required to incur material additional expense in preparing such information.

The KPI Dashboard shall be delivered electronically to such email addresses as the Investor may designate in writing to the Company from time to time, or through such secure document-sharing platform as the Investor may designate in writing, provided that the Company shall not be required to adopt any platform that would impose an unreasonable cost or administrative burden on the Company. The initial delivery address shall be as set forth in Section 11 below.

2(b) Cap Table Access.

The Company shall provide the Investor with continuous access to the Company's current capitalization table, maintained on a fully-diluted basis, through the Company's capitalization table management platform (e.g., Sterling Reach Health IT, Pulley, or a comparable service). If the Company does not maintain a cap table management platform or if such platform does not permit investor access, the Company shall deliver to the Investor an updated capitalization table in spreadsheet format (Microsoft Excel or comparable format) within five (5) business days following any event that changes the Company's capitalization, including but not limited to:

(i) the grant, exercise, early exercise, repurchase, cancellation, expiration, or forfeiture of options under the 2024 Equity Incentive Plan (or any successor plan);

(ii) the issuance of new shares of Common Stock, Preferred Stock, or any other class or series of equity securities of the Company;

(iii) the issuance, conversion, exchange, or cancellation of any convertible instruments, including convertible promissory notes, SAFEs, or other similar instruments;

(iv) any stock split, stock dividend, combination, recapitalization, or similar event; and

(v) any repurchase, redemption, or cancellation of outstanding shares.

The capitalization table shall reflect all classes of equity securities of the Company, including Common Stock, Series Seed Preferred Stock, and the option pool under the 2024 Equity Incentive Plan (which, as of the date hereof, consists of 1,600,000 shares in the aggregate, of which 175,000 shares are subject to outstanding option grants and 1,425,000 shares remain unallocated and available for future grants), as well as any warrants, convertible instruments, or other rights to acquire equity securities of the Company.

The Investor and its representatives shall treat all capitalization information received pursuant to this Section 2(b) as Confidential Information in accordance with Section 8 of this Side Letter, and shall not disclose such information to any third party except as expressly permitted under Section 8.

3. BOARD OBSERVER RIGHT

3.1 Appointment of Observer. The Company shall permit one (1) additional representative designated by the Investor (the "Observer") to attend all regular and special meetings of the Board in a nonvoting, observer capacity. For the avoidance of doubt, this Observer right is in addition to, and not in lieu of, the Investor's right under the Voting Agreement to designate one (1) member of the Board to serve as the Series Seed Preferred Stock director. As of the date hereof, the Investor's designated Board member is David Hargrove, Partner at Cobalt Ventures LP.

3.2 Access to Board Materials. The Observer shall be entitled to receive all written materials, notices, agendas, board packages, minutes, and other information provided to the directors of the Board, at the same time and in the same manner as such materials are provided to the directors, including any materials distributed in advance of, during, or following any meeting of the Board.

3.3 Exclusion. Notwithstanding the foregoing, the Company may exclude the Observer from any portion of a Board meeting or from receipt of any specific materials if:

(i) the Company's legal counsel advises in writing (which may be by email to the Company's Chief Executive Officer) that such exclusion is reasonably necessary to preserve the attorney-client privilege or work product protection applicable to the matter being discussed or the materials at issue; or

(ii) the Board determines in good faith, by a majority vote of the disinterested directors present and voting, that the Observer has an actual conflict of interest with respect to the specific matter being discussed or addressed in such materials.

In the event that the Observer is excluded from any portion of a Board meeting or from receipt of any materials pursuant to this Section 3.3, the Company shall promptly notify the Investor of the general subject matter of the excluded discussion or materials and the basis for exclusion, to the extent such disclosure would not itself compromise the privilege or exacerbate the conflict giving rise to the exclusion.

3.4 Confidentiality. The Observer shall, prior to attending any Board meeting or receiving any Board materials, execute such confidentiality and non-disclosure agreement as the Company may reasonably request, in a form consistent with the confidentiality obligations set forth in this Side Letter and the IRA.

3.5 Designation and Replacement. The initial Observer shall be designated by the Investor in writing to the Company within fifteen (15) days following the date hereof. The Investor may change the identity of the Observer at any time by providing written notice to the Company, and any such replacement Observer shall be required to execute the confidentiality agreement referenced in Section 3.4 prior to attending any Board meeting or receiving any Board materials.

4. MOST FAVORED NATION CLAUSE

4.1 MFN Right. If the Company enters into any side letter agreement, supplemental agreement, or similar arrangement (whether written or oral, and whether characterized as a side letter, supplement, amendment, or otherwise) with any other investor in the Financing (including, without limitation, Pinewood Health Ventures, LLC, Thornfield Capital Partners, LP, or Atlas Point Angel Syndicate, LLC) or with any future investor in the Company, that grants such other investor rights or terms that are, individually or in the aggregate, more favorable to such investor than the rights and terms granted to the Investor under this Side Letter and/or the Transaction Documents, the Company shall promptly (and in no event later than five (5) business days after execution or entry into such agreement or arrangement) notify the Investor in writing and provide the Investor with a complete and unredacted copy of such agreement or arrangement.

4.2 Deemed Amendment. Upon written request by the Investor delivered to the Company within thirty (30) days of the Investor's receipt of the notice and copy described in Section 4.1 above, this Side Letter and/or the applicable Transaction Document(s) shall be deemed automatically amended, without the requirement of any further action by the Parties, to incorporate such more favorable rights or terms for the benefit of the Investor, effective as of the date such more favorable rights or terms were first granted to the other investor. The Company shall, at the request of the Investor, promptly execute and deliver any written amendments or confirmations necessary to evidence or effectuate such deemed amendment.

4.3 Current Disclosure. The Company represents and warrants to the Investor that, as of the date hereof, the only other side letter or supplemental agreement executed in connection with the Financing is that certain side letter agreement with Pinewood Health Ventures, LLC (the "Pinewood Side Letter"), which contains (i) a most favored nation clause substantially similar to this Section 4 and (ii) a co-investment right permitting Pinewood Health Ventures, LLC to invest up to $1,500,000 in the next Qualified Financing of the Company. The Company further represents and warrants that the Pinewood Side Letter does not contain any rights or terms that are more favorable to Pinewood Health Ventures, LLC than the rights and terms granted to the Investor under this Side Letter and the Transaction Documents.

5. ANNUAL DATA PRIVACY AND SECURITY COMPLIANCE AUDIT RIGHT

5.1 Audit Right. The Investor shall have the right, exercisable no more than one (1) time during each twelve (12)-month period during the term of this Side Letter, to conduct or cause to be conducted (through qualified third-party auditors, consultants, or other professionals selected by the Investor) a compliance audit of the Company's data privacy and security practices (each, an "Audit"). The cost and expense of each Audit shall be borne by the Investor; provided, however, that if any Audit reveals a material deficiency (as reasonably determined by the Investor), the Company shall bear the reasonable and documented out-of-pocket cost of such Audit.

5.2 Audit Scope. The scope of each Audit shall include, without limitation, a review and assessment of the following:

(i) the Company's compliance with applicable data privacy and security laws, rules, and regulations, including but not limited to the Health Insurance Portability and Accountability Act of 1996 ("HIPAA"), as amended by the Health Information Technology for Economic and Clinical Health Act ("HITECH"), and implementing regulations, and applicable state privacy and data protection laws, in each case to the extent applicable to the Company's diagnostic health data collection, processing, storage, and transmission activities in connection with the MeridianPulse platform and related products and services;

(ii) the Company's information security policies, procedures, standards, and technical safeguards, including without limitation access controls, encryption practices, network security, vulnerability management, and third-party vendor security assessments;

(iii) the Company's incident response planning, breach notification procedures, and business continuity and disaster recovery protocols;

(iv) the status and adequacy of any business associate agreements ("BAAs") entered into by the Company with third-party service providers, data processors, or other parties who receive, access, or process protected health information or other sensitive data on behalf of the Company;

(v) employee and contractor training programs related to data privacy, security awareness, and HIPAA compliance, including the frequency, content, and participation records of such training; and

(vi) cybersecurity posture assessments, including penetration testing results (if available), security audit reports, and the status of any known or suspected vulnerabilities or security incidents.

5.3 Company Cooperation. The Company shall provide reasonable cooperation and access to the Investor and its designated auditors, consultants, or other representatives in connection with each Audit, including access to relevant personnel (including the Company's Chief Technology Officer, Chief Information Security Officer or equivalent, and legal and compliance personnel), systems documentation, security policies, audit logs, and facilities. Such access shall be subject to reasonable scheduling accommodations and scope limitations to avoid undue disruption to the Company's business operations.

5.4 Notice. The Investor shall provide at least thirty (30) days' prior written notice to the Company before commencing any Audit. Such notice shall specify the proposed scope, timing, and duration of the Audit, and the identity of the auditors or consultants who will conduct the Audit. The Company may object to any proposed auditor or consultant on reasonable grounds (including conflicts of interest), and the Parties shall cooperate in good faith to resolve any such objection. The Investor shall use commercially reasonable efforts to minimize disruption to the Company's business operations in connection with any Audit.

5.5 Confidentiality of Audit Materials. All audit findings, reports, workpapers, and related materials generated in connection with any Audit (collectively, "Audit Materials") shall be treated as Confidential Information of the Company under Section 8 of this Side Letter. The Investor shall not disclose any Audit Materials to any third party without the Company's prior written consent, except:

(i) to the Investor's general partner (Cobalt Ventures GP III, LLC), limited partners, legal counsel (including Calderwood & Harkness LLP), and professional advisors, in each case on a need-to-know basis and subject to obligations of confidentiality no less protective than those set forth in Section 8; or

(ii) as required by applicable law, regulation, or legal process.

5.6 Remediation. If any Audit reveals a material deficiency in the Company's data privacy or security practices, the Company shall prepare and deliver to the Investor a written remediation plan within thirty (30) days following receipt of the Audit findings. Such remediation plan shall describe in reasonable detail the nature of the deficiency, the proposed corrective actions, and a timeline for implementation. The Company shall use commercially reasonable efforts to remediate any material deficiency within ninety (90) days following delivery of the remediation plan (or such longer period as may be reasonably required given the nature and complexity of the deficiency, provided the Company is diligently pursuing remediation and provides the Investor with periodic status updates no less frequently than monthly until the deficiency has been fully remediated).

6. CONSENT RIGHT OVER SIGNIFICANT EXPENDITURES

6.1 Consent Requirement. The Company shall not make, commit to, or authorize any single expenditure or series of related expenditures in excess of Two Hundred Thousand Dollars ($200,000) without the prior written consent of the Investor (which consent shall not be unreasonably withheld, conditioned, or delayed). For purposes of this Section 6, "single expenditure" includes any capital expenditure, operating expense, contract commitment, settlement payment, or other outlay of funds, whether in cash or in kind, and "series of related expenditures" means two or more expenditures that are related by subject matter, counterparty, project, or purpose and that, when aggregated, exceed the $200,000 threshold.

6.2 Relationship to Other Approval Rights. This consent right is in addition to, and not in limitation of, any protective provisions set forth in the Company's Amended and Restated Certificate of Incorporation (including, without limitation, the requirement of the consent of the holders of a majority of the outstanding shares of Series Seed Preferred Stock, voting as a separate class, for (a) the incurrence of indebtedness in excess of $250,000 outside the ordinary course of business, (b) acquisitions of other businesses or entities in excess of $500,000, and (c) related-party transactions in excess of $100,000), and any board approval requirements under applicable law, the Company's bylaws, or the Transaction Documents.

6.3 Notice and Information. The Company shall provide the Investor with reasonable advance notice (not less than five (5) business days) of any proposed expenditure subject to this Section 6, together with sufficient detail regarding the proposed expenditure to allow the Investor to make an informed decision, including the amount, purpose, proposed counterparty (if applicable), expected timing, and the Company's rationale for the expenditure.

6.4 Deemed Consent. If the Investor does not respond in writing (including by email) to the Company's request for consent within ten (10) business days of receiving complete information regarding a proposed expenditure pursuant to Section 6.3, the Investor shall be deemed to have consented to such expenditure.

6.5 Exceptions. Notwithstanding the foregoing, the consent right set forth in this Section 6 shall not apply to:

(i) payroll and employee benefit obligations incurred in the ordinary course of business consistent with the Company's approved annual budget (as approved by the Board);

(ii) rent and lease payments under existing lease agreements to which the Company is a party as of the date hereof, as well as utility and common area maintenance charges arising under such agreements; or

(iii) expenditures that have been specifically identified and approved by the Board in the Company's annual budget for the applicable fiscal year, provided that the actual expenditure does not exceed the budgeted amount for such line item by more than ten percent (10%).

7. TERM AND TERMINATION

7.1 Effective Date. This Side Letter shall become effective as of the date first written above (February 9, 2026).

7.2 Termination. This Side Letter shall remain in full force and effect until the earliest to occur of:

(i) the mutual written agreement of the Company and the Investor to terminate this Side Letter;

(ii) the closing of a Qualified IPO (as defined in the Company's Amended and Restated Certificate of Incorporation);

(iii) the closing of a Deemed Liquidation Event (as defined in the Company's Amended and Restated Certificate of Incorporation); or

(iv) such time as the Investor (together with its affiliates) no longer holds any shares of Series Seed Preferred Stock of the Company (or shares of Common Stock issued upon conversion thereof).

7.3 Survival. Notwithstanding the foregoing, Section 8 (Confidentiality) and Section 10 (Governing Law; Dispute Resolution) shall survive the termination or expiration of this Side Letter in accordance with their respective terms.

8. CONFIDENTIALITY

8.1 General Obligation. The terms and provisions of this Side Letter are confidential and shall not be disclosed by either Party to any third party without the prior written consent of the other Party, except as expressly provided in this Section 8.

8.2 Permitted Disclosures. Notwithstanding Section 8.1, either Party may disclose the terms and provisions of this Side Letter:

(i) to such Party's respective legal counsel, accountants, auditors, and professional advisors (including, with respect to the Investor, Calderwood & Harkness LLP and Morgan Tsai, VP of Legal Affairs of Cobalt Ventures LP), in each case on a need-to-know basis and subject to obligations of confidentiality no less protective than those set forth herein;

(ii) with respect to the Investor, to the Investor's general partner (Cobalt Ventures GP III, LLC), its limited partners, and its affiliates, on a need-to-know basis and subject to obligations of confidentiality no less protective than those set forth herein;

(iii) as required by applicable law, regulation, or legal process, provided that the disclosing Party shall, to the extent permitted by law, provide the other Party with prompt written notice of any such required disclosure and shall cooperate with the other Party in seeking a protective order or other appropriate remedy; or

(iv) to the extent necessary in connection with the enforcement of rights under this Side Letter or any of the Transaction Documents.

8.3 Information Received Under This Side Letter. All information received by the Investor, its Observer, or its representatives pursuant to Section 2 (Additional Information Rights) and Section 5 (Annual Data Privacy and Security Compliance Audit Right) of this Side Letter shall be treated as confidential and proprietary information of the Company and shall be subject to the confidentiality obligations set forth in this Section 8 and, to the extent applicable, the confidentiality provisions of the IRA.

9. RELATIONSHIP TO TRANSACTION DOCUMENTS

9.1 Supplemental Agreement. This Side Letter is supplemental to, and shall be read together with, the Transaction Documents. The execution and delivery of this Side Letter is a condition to the closing of the transactions contemplated by the Purchase Agreement.

9.2 Conflict. In the event of any conflict or inconsistency between the terms of this Side Letter and the terms of the Purchase Agreement, the IRA, the Voting Agreement, or the ROFR Agreement, the terms of this Side Letter shall control with respect to the Investor, but only to the extent of such conflict or inconsistency.

9.3 No Modification of Other Investors' Rights. This Side Letter shall not be construed to modify, amend, or otherwise affect the rights, obligations, or privileges of any investor other than the Investor under any of the Transaction Documents.

9.4 Preservation of Investor Rights. Nothing in this Side Letter shall be construed to diminish, limit, or waive any rights of the Investor under the Transaction Documents. All rights granted to the Investor hereunder are in addition to, and not in limitation of, any rights granted to the Investor under the Purchase Agreement, the IRA, the Voting Agreement, and the ROFR Agreement.

10. GOVERNING LAW; DISPUTE RESOLUTION

10.1 Governing Law. This Side Letter shall be governed by and construed in accordance with the internal laws of the State of Delaware, without giving effect to the principles of conflicts of law thereof that would require or permit the application of the laws of any other jurisdiction.

10.2 Dispute Resolution. Any dispute, controversy, or claim arising out of or relating to this Side Letter, or the breach, termination, or validity thereof, shall be resolved in accordance with the dispute resolution provisions set forth in Section 9 of the Purchase Agreement, which provisions are hereby incorporated by reference and shall apply mutatis mutandis to this Side Letter.

11. NOTICES

All notices, requests, demands, consents, and other communications required or permitted under this Side Letter shall be in writing and shall be delivered in accordance with the notice provisions set forth in Section 7 of the Purchase Agreement. Without limiting the foregoing, notices shall be sent to the following addresses (or to such other address as a Party may designate by written notice to the other Party in accordance with this Section 11):

If to the Company:

Meridian Diagnostics, Inc. 225 Binney Street, Suite 400 Cambridge, MA 02142

Attention: Dr. Priya Ramaswamy, Chief Executive Officer & President

Email: pramaswamy@meridiandiagnostics.com

with a copy (which shall not constitute notice) to:

Whitfield & Ames LLP 100 Federal Street, 30th Floor Boston, MA 02110

Attention: Catherine Devereaux

Email: cdevereaux@whitfieldames.com

If to the Investor:

Cobalt Ventures Fund III, LP c/o Cobalt Ventures LP 2400 Sand Hill Road, Suite 310 Menlo Park, CA 94025

Attention: Elaine Cho, Managing Partner, and Morgan Tsai, VP of Legal Affairs

Email: echo@cobaltventures.com; mtsai@cobaltventures.com

with a copy (which shall not constitute notice) to:

Calderwood & Harkness LLP 1800 Page Mill Road, Suite 200 Menlo Park, CA 94025

Attention: Kevin Ostrowski

Email: kostrowski@calderwoodharkness.com

12. AMENDMENTS AND WAIVERS

12.1 Amendments. This Side Letter may be amended, modified, or supplemented only by a written instrument executed and delivered by both the Company and the Investor. No oral agreement, course of dealing, or trade usage shall be effective to amend, modify, or supplement the terms of this Side Letter.

12.2 Waivers. No waiver of any provision of this Side Letter, or of any right or remedy hereunder, shall be effective unless set forth in a written instrument signed by the Party to be bound thereby. No waiver of any provision shall constitute a waiver of any other provision, nor shall any waiver of any provision on one occasion constitute a waiver of such provision on any future occasion. The failure or delay of either Party in exercising any right, power, or privilege under this Side Letter shall not operate as a waiver thereof.

13. ASSIGNMENT

This Side Letter and the rights and obligations hereunder may not be assigned or transferred by either Party without the prior written consent of the other Party, which consent may be granted or withheld in such Party's sole discretion; provided, however, that the Investor may, without the prior written consent of the Company, assign its rights (but not its obligations, except in connection with a transfer of shares as described below) under this Side Letter to:

(a) any affiliate of the Investor (as defined in Rule 405 under the Securities Act of 1933, as amended); or

(b) any transferee of all or substantially all of the Investor's shares of Series Seed Preferred Stock (or Common Stock issued upon conversion thereof) of the Company, provided that such transferee agrees in writing, in a form reasonably satisfactory to the Company, to be bound by the terms and conditions of this Side Letter as if such transferee were the original "Investor" hereunder.

Any attempted assignment in violation of this Section 13 shall be null and void and of no force or effect.

14. ENTIRE AGREEMENT

This Side Letter, together with the Transaction Documents (including all exhibits, schedules, and annexes thereto), constitutes the entire agreement between the Parties with respect to the subject matter hereof and supersedes all prior and contemporaneous negotiations, discussions, proposals, agreements, representations, warranties, and understandings, whether written or oral, relating to the subject matter hereof. Neither Party has relied upon any statement, representation, warranty, or agreement of the other Party except for those expressly set forth in this Side Letter and the Transaction Documents.

15. COUNTERPARTS; ELECTRONIC SIGNATURES

This Side Letter may be executed in one or more counterparts, each of which shall be deemed an original and all of which, taken together, shall constitute one and the same instrument. The exchange of executed counterparts of this Side Letter by electronic means (including by PDF transmitted via email or by electronic signature platform such as DocuSign or similar service) shall be sufficient to bind the Parties, and such electronic copies or signatures shall be deemed original signatures for all purposes and shall be admissible in any legal proceeding arising under or in connection with this Side Letter.

16. SEVERABILITY

If any provision of this Side Letter, or the application of any such provision to any person, entity, or circumstance, shall be held to be invalid, illegal, or unenforceable by a court of competent jurisdiction, the remainder of this Side Letter and the application of such provision to other persons, entities, or circumstances shall not be affected thereby, and each remaining provision of this Side Letter shall be valid and enforceable to the fullest extent permitted by applicable law. In the event that any provision is so held to be invalid, illegal, or unenforceable, the Parties shall negotiate in good faith to replace such provision with a valid, legal, and enforceable provision that, to the greatest extent possible, achieves the original intent and economic effect of the invalid, illegal, or unenforceable provision.

[Signature Page Follows]

IN WITNESS WHEREOF, the Parties have executed this Side Letter Agreement as of the date first written above.

MERIDIAN DIAGNOSTICS, INC.

By: ________

Name: Dr. Priya Ramaswamy

Title: Chief Executive Officer & President

Date: February 9, 2026

COBALT VENTURES FUND III, LP

By: Cobalt Ventures GP III, LLC, its General Partner

By: ________

Name: Elaine Cho

Title: Managing Partner

Date: February 9, 2026

[Signature Page to Side Letter Agreement]

SIDE LETTER AGREEMENT
Side Letter to the Series Seed Preferred Stock Purchase Agreement dated February 9, 2026
February 9, 2026
This Side Letter Agreement (this "Side Letter") is entered into as of February 9, 2026, by and between:
MERIDIAN DIAGNOSTICS, INC., a Delaware corporation (the "Company"), with its principal office located at 225 Binney Street, Suite 400, Cambridge, MA 02142;
and
COBALT VENTURES FUND III, LP, a Delaware limited partnership (the "Investor"), acting through its general partner, Cobalt Ventures GP III, LLC, a Delaware limited liability company, with its principal office located at 2400 Sand Hill Road, Suite 310, Menlo Park, CA 94025.
The Company and the Investor are each referred to herein individually as a "Party" and collectively as the "Parties."
RECITALS
WHEREAS, the Company and the Investor are parties to that certain Series Seed Preferred Stock Purchase Agreement, dated as of February 9, 2026 (the "Purchase Agreement"), pursuant to which the Investor is purchasing 2,687,989 shares of Series Seed Preferred Stock of the Company at a price per share of $2.6786, for aggregate consideration of Seven Million Two Hundred Thousand Dollars ($7,200,000), as part of an aggregate financing round of Twelve Million Dollars ($12,000,000) (the "Financing");
WHEREAS, the Company and the Investor are also parties to that certain Investors' Rights Agreement dated as of the date hereof (the "IRA"), that certain Voting Agreement dated as of the date hereof (the "Voting Agreement"), and that certain Right of First Refusal and Co-Sale Agreement dated as of the date hereof (the "ROFR Agreement," and together with the Purchase Agreement, the IRA, the Voting Agreement, and this Side Letter, the "Transaction Documents");
WHEREAS, as a condition to the Investor's obligations under the Purchase Agreement, the Company has agreed to provide the Investor with certain additional rights and protections as set forth herein;
WHEREAS, the Investor is the lead investor in the Financing, committing $7,200,000 (representing 60.0% of the aggregate round size), and such additional rights reflect the Investor's significant capital commitment and leadership role in the transaction; and
NOW, THEREFORE, in consideration of the mutual promises and covenants contained herein and the Investor's purchase of shares under the Purchase Agreement, and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the Parties agree as follows:
1. DEFINITIONS
1.1 Generally. Capitalized terms used but not otherwise defined in this Side Letter shall have the meanings ascribed to such terms in the Purchase Agreement or, if not defined therein, in the IRA.
1.2 Defined Terms. As used in this Side Letter, the following terms shall have the following meanings:
(a) "Board" means the Board of Directors of the Company, as constituted from time to time in accordance with the Company's Amended and Restated Certificate of Incorporation and the Voting Agreement.
(b) "Investor Designee" means any individual designated by the Investor to serve as a board observer pursuant to Section 3 of this Side Letter.
(c) "KPI Dashboard" has the meaning set forth in Section 2(a) below.
(d) "Major Investor" has the meaning set forth in the IRA, which, as of the date hereof, means any holder of at least 1,000,000 shares of Series Seed Preferred Stock (or Common Stock issued upon conversion thereof), as adjusted for any stock splits, stock dividends, combinations, recapitalizations, or similar events.
(e) "Observer" has the meaning set forth in Section 3 below.
(f) "Qualified Financing" has the meaning set forth in the Purchase Agreement and the IRA, as applicable.
2. ADDITIONAL INFORMATION RIGHTS
2(a) Monthly KPI Dashboard.
In addition to the information rights granted to Major Investors under Section 3.1 of the IRA (which include, among other things, annual audited financial statements, quarterly unaudited financial statements, monthly management reports, and an annual budget and business plan), the Company shall prepare and deliver to the Investor a monthly key performance indicator dashboard (the "KPI Dashboard") within fifteen (15) days following the end of each calendar month. The KPI Dashboard shall include, at a minimum, the following categories of information:
(i) Cash and Burn. The Company's cash balance as of the end of such calendar month and the Company's monthly cash burn rate for such calendar month (for reference, as of the date hereof the Company's approximate monthly burn rate is $185,000);
(ii) Revenue. Revenue recognized during such calendar month, if any, and year-to-date revenue, together with a brief narrative of material revenue developments;
(iii) Headcount. Total headcount as of the end of such calendar month, broken down by department or functional area, including identification of any new hires or departures (for reference, as of the date hereof the Company employs 18 full-time employees);
(iv) Product Development. Progress updates on product development milestones for the MeridianPulse platform, including the Company's 14-marker point-of-care blood panel with a target sub-8-minute turnaround time, as well as any material changes to the product roadmap or timeline;
(v) Clinical and Regulatory. Clinical trial status updates and regulatory submissions, approvals, or material communications with the U.S. Food and Drug Administration or other applicable regulatory authorities;
(vi) Pipeline Metrics. Key customer acquisition and partnership pipeline metrics, including the number of active prospective customer or partner discussions, any executed letters of intent or term sheets, and material changes to existing commercial relationships; and
(vii) Other Metrics. Such other metrics or information as the Investor may reasonably request from time to time upon not less than ten (10) business days' prior written notice to the Company, provided that the Company shall not be required to incur material additional expense in preparing such information.
The KPI Dashboard shall be delivered electronically to such email addresses as the Investor may designate in writing to the Company from time to time, or through such secure document-sharing platform as the Investor may designate in writing, provided that the Company shall not be required to adopt any platform that would impose an unreasonable cost or administrative burden on the Company. The initial delivery address shall be as set forth in Section 11 below.
2(b) Cap Table Access.
The Company shall provide the Investor with continuous access to the Company's current capitalization table, maintained on a fully-diluted basis, through the Company's capitalization table management platform (e.g., Sterling Reach Health IT, Pulley, or a comparable service). If the Company does not maintain a cap table management platform or if such platform does not permit investor access, the Company shall deliver to the Investor an updated capitalization table in spreadsheet format (Microsoft Excel or comparable format) within five (5) business days following any event that changes the Company's capitalization, including but not limited to:
(i) the grant, exercise, early exercise, repurchase, cancellation, expiration, or forfeiture of options under the 2024 Equity Incentive Plan (or any successor plan);
(ii) the issuance of new shares of Common Stock, Preferred Stock, or any other class or series of equity securities of the Company;
(iii) the issuance, conversion, exchange, or cancellation of any convertible instruments, including convertible promissory notes, SAFEs, or other similar instruments;
(iv) any stock split, stock dividend, combination, recapitalization, or similar event; and
(v) any repurchase, redemption, or cancellation of outstanding shares.
The capitalization table shall reflect all classes of equity securities of the Company, including Common Stock, Series Seed Preferred Stock, and the option pool under the 2024 Equity Incentive Plan (which, as of the date hereof, consists of 1,600,000 shares in the aggregate, of which 175,000 shares are subject to outstanding option grants and 1,425,000 shares remain unallocated and available for future grants), as well as any warrants, convertible instruments, or other rights to acquire equity securities of the Company.
The Investor and its representatives shall treat all capitalization information received pursuant to this Section 2(b) as Confidential Information in accordance with Section 8 of this Side Letter, and shall not disclose such information to any third party except as expressly permitted under Section 8.
3. BOARD OBSERVER RIGHT
3.1 Appointment of Observer. The Company shall permit one (1) additional representative designated by the Investor (the "Observer") to attend all regular and special meetings of the Board in a nonvoting, observer capacity. For the avoidance of doubt, this Observer right is in addition to, and not in lieu of, the Investor's right under the Voting Agreement to designate one (1) member of the Board to serve as the Series Seed Preferred Stock director. As of the date hereof, the Investor's designated Board member is David Hargrove, Partner at Cobalt Ventures LP.
3.2 Access to Board Materials. The Observer shall be entitled to receive all written materials, notices, agendas, board packages, minutes, and other information provided to the directors of the Board, at the same time and in the same manner as such materials are provided to the directors, including any materials distributed in advance of, during, or following any meeting of the Board.
3.3 Exclusion. Notwithstanding the foregoing, the Company may exclude the Observer from any portion of a Board meeting or from receipt of any specific materials if:
(i) the Company's legal counsel advises in writing (which may be by email to the Company's Chief Executive Officer) that such exclusion is reasonably necessary to preserve the attorney-client privilege or work product protection applicable to the matter being discussed or the materials at issue; or
(ii) the Board determines in good faith, by a majority vote of the disinterested directors present and voting, that the Observer has an actual conflict of interest with respect to the specific matter being discussed or addressed in such materials.
In the event that the Observer is excluded from any portion of a Board meeting or from receipt of any materials pursuant to this Section 3.3, the Company shall promptly notify the Investor of the general subject matter of the excluded discussion or materials and the basis for exclusion, to the extent such disclosure would not itself compromise the privilege or exacerbate the conflict giving rise to the exclusion.
3.4 Confidentiality. The Observer shall, prior to attending any Board meeting or receiving any Board materials, execute such confidentiality and non-disclosure agreement as the Company may reasonably request, in a form consistent with the confidentiality obligations set forth in this Side Letter and the IRA.
3.5 Designation and Replacement. The initial Observer shall be designated by the Investor in writing to the Company within fifteen (15) days following the date hereof. The Investor may change the identity of the Observer at any time by providing written notice to the Company, and any such replacement Observer shall be required to execute the confidentiality agreement referenced in Section 3.4 prior to attending any Board meeting or receiving any Board materials.
4. MOST FAVORED NATION CLAUSE
4.1 MFN Right. If the Company enters into any side letter agreement, supplemental agreement, or similar arrangement (whether written or oral, and whether characterized as a side letter, supplement, amendment, or otherwise) with any other investor in the Financing (including, without limitation, Pinewood Health Ventures, LLC, Thornfield Capital Partners, LP, or Atlas Point Angel Syndicate, LLC) or with any future investor in the Company, that grants such other investor rights or terms that are, individually or in the aggregate, more favorable to such investor than the rights and terms granted to the Investor under this Side Letter and/or the Transaction Documents, the Company shall promptly (and in no event later than five (5) business days after execution or entry into such agreement or arrangement) notify the Investor in writing and provide the Investor with a complete and unredacted copy of such agreement or arrangement.
4.2 Deemed Amendment. Upon written request by the Investor delivered to the Company within thirty (30) days of the Investor's receipt of the notice and copy described in Section 4.1 above, this Side Letter and/or the applicable Transaction Document(s) shall be deemed automatically amended, without the requirement of any further action by the Parties, to incorporate such more favorable rights or terms for the benefit of the Investor, effective as of the date such more favorable rights or terms were first granted to the other investor. The Company shall, at the request of the Investor, promptly execute and deliver any written amendments or confirmations necessary to evidence or effectuate such deemed amendment.
4.3 Current Disclosure. The Company represents and warrants to the Investor that, as of the date hereof, the only other side letter or supplemental agreement executed in connection with the Financing is that certain side letter agreement with Pinewood Health Ventures, LLC (the "Pinewood Side Letter"), which contains (i) a most favored nation clause substantially similar to this Section 4 and (ii) a co-investment right permitting Pinewood Health Ventures, LLC to invest up to $1,500,000 in the next Qualified Financing of the Company. The Company further represents and warrants that the Pinewood Side Letter does not contain any rights or terms that are more favorable to Pinewood Health Ventures, LLC than the rights and terms granted to the Investor under this Side Letter and the Transaction Documents.
5. ANNUAL DATA PRIVACY AND SECURITY COMPLIANCE AUDIT RIGHT
5.1 Audit Right. The Investor shall have the right, exercisable no more than one (1) time during each twelve (12)-month period during the term of this Side Letter, to conduct or cause to be conducted (through qualified third-party auditors, consultants, or other professionals selected by the Investor) a compliance audit of the Company's data privacy and security practices (each, an "Audit"). The cost and expense of each Audit shall be borne by the Investor; provided, however, that if any Audit reveals a material deficiency (as reasonably determined by the Investor), the Company shall bear the reasonable and documented out-of-pocket cost of such Audit.
5.2 Audit Scope. The scope of each Audit shall include, without limitation, a review and assessment of the following:
(i) the Company's compliance with applicable data privacy and security laws, rules, and regulations, including but not limited to the Health Insurance Portability and Accountability Act of 1996 ("HIPAA"), as amended by the Health Information Technology for Economic and Clinical Health Act ("HITECH"), and implementing regulations, and applicable state privacy and data protection laws, in each case to the extent applicable to the Company's diagnostic health data collection, processing, storage, and transmission activities in connection with the MeridianPulse platform and related products and services;
(ii) the Company's information security policies, procedures, standards, and technical safeguards, including without limitation access controls, encryption practices, network security, vulnerability management, and third-party vendor security assessments;
(iii) the Company's incident response planning, breach notification procedures, and business continuity and disaster recovery protocols;
(iv) the status and adequacy of any business associate agreements ("BAAs") entered into by the Company with third-party service providers, data processors, or other parties who receive, access, or process protected health information or other sensitive data on behalf of the Company;
(v) employee and contractor training programs related to data privacy, security awareness, and HIPAA compliance, including the frequency, content, and participation records of such training; and
(vi) cybersecurity posture assessments, including penetration testing results (if available), security audit reports, and the status of any known or suspected vulnerabilities or security incidents.
5.3 Company Cooperation. The Company shall provide reasonable cooperation and access to the Investor and its designated auditors, consultants, or other representatives in connection with each Audit, including access to relevant personnel (including the Company's Chief Technology Officer, Chief Information Security Officer or equivalent, and legal and compliance personnel), systems documentation, security policies, audit logs, and facilities. Such access shall be subject to reasonable scheduling accommodations and scope limitations to avoid undue disruption to the Company's business operations.
5.4 Notice. The Investor shall provide at least thirty (30) days' prior written notice to the Company before commencing any Audit. Such notice shall specify the proposed scope, timing, and duration of the Audit, and the identity of the auditors or consultants who will conduct the Audit. The Company may object to any proposed auditor or consultant on reasonable grounds (including conflicts of interest), and the Parties shall cooperate in good faith to resolve any such objection. The Investor shall use commercially reasonable efforts to minimize disruption to the Company's business operations in connection with any Audit.
5.5 Confidentiality of Audit Materials. All audit findings, reports, workpapers, and related materials generated in connection with any Audit (collectively, "Audit Materials") shall be treated as Confidential Information of the Company under Section 8 of this Side Letter. The Investor shall not disclose any Audit Materials to any third party without the Company's prior written consent, except:
(i) to the Investor's general partner (Cobalt Ventures GP III, LLC), limited partners, legal counsel (including Calderwood & Harkness LLP), and professional advisors, in each case on a need-to-know basis and subject to obligations of confidentiality no less protective than those set forth in Section 8; or
(ii) as required by applicable law, regulation, or legal process.
5.6 Remediation. If any Audit reveals a material deficiency in the Company's data privacy or security practices, the Company shall prepare and deliver to the Investor a written remediation plan within thirty (30) days following receipt of the Audit findings. Such remediation plan shall describe in reasonable detail the nature of the deficiency, the proposed corrective actions, and a timeline for implementation. The Company shall use commercially reasonable efforts to remediate any material deficiency within ninety (90) days following delivery of the remediation plan (or such longer period as may be reasonably required given the nature and complexity of the deficiency, provided the Company is diligently pursuing remediation and provides the Investor with periodic status updates no less frequently than monthly until the deficiency has been fully remediated).
6. CONSENT RIGHT OVER SIGNIFICANT EXPENDITURES
6.1 Consent Requirement. The Company shall not make, commit to, or authorize any single expenditure or series of related expenditures in excess of Two Hundred Thousand Dollars ($200,000) without the prior written consent of the Investor (which consent shall not be unreasonably withheld, conditioned, or delayed). For purposes of this Section 6, "single expenditure" includes any capital expenditure, operating expense, contract commitment, settlement payment, or other outlay of funds, whether in cash or in kind, and "series of related expenditures" means two or more expenditures that are related by subject matter, counterparty, project, or purpose and that, when aggregated, exceed the $200,000 threshold.
6.2 Relationship to Other Approval Rights. This consent right is in addition to, and not in limitation of, any protective provisions set forth in the Company's Amended and Restated Certificate of Incorporation (including, without limitation, the requirement of the consent of the holders of a majority of the outstanding shares of Series Seed Preferred Stock, voting as a separate class, for (a) the incurrence of indebtedness in excess of $250,000 outside the ordinary course of business, (b) acquisitions of other businesses or entities in excess of $500,000, and (c) related-party transactions in excess of $100,000), and any board approval requirements under applicable law, the Company's bylaws, or the Transaction Documents.
6.3 Notice and Information. The Company shall provide the Investor with reasonable advance notice (not less than five (5) business days) of any proposed expenditure subject to this Section 6, together with sufficient detail regarding the proposed expenditure to allow the Investor to make an informed decision, including the amount, purpose, proposed counterparty (if applicable), expected timing, and the Company's rationale for the expenditure.
6.4 Deemed Consent. If the Investor does not respond in writing (including by email) to the Company's request for consent within ten (10) business days of receiving complete information regarding a proposed expenditure pursuant to Section 6.3, the Investor shall be deemed to have consented to such expenditure.
6.5 Exceptions. Notwithstanding the foregoing, the consent right set forth in this Section 6 shall not apply to:
(i) payroll and employee benefit obligations incurred in the ordinary course of business consistent with the Company's approved annual budget (as approved by the Board);
(ii) rent and lease payments under existing lease agreements to which the Company is a party as of the date hereof, as well as utility and common area maintenance charges arising under such agreements; or
(iii) expenditures that have been specifically identified and approved by the Board in the Company's annual budget for the applicable fiscal year, provided that the actual expenditure does not exceed the budgeted amount for such line item by more than ten percent (10%).
7. TERM AND TERMINATION
7.1 Effective Date. This Side Letter shall become effective as of the date first written above (February 9, 2026).
7.2 Termination. This Side Letter shall remain in full force and effect until the earliest to occur of:
(i) the mutual written agreement of the Company and the Investor to terminate this Side Letter;
(ii) the closing of a Qualified IPO (as defined in the Company's Amended and Restated Certificate of Incorporation);
(iii) the closing of a Deemed Liquidation Event (as defined in the Company's Amended and Restated Certificate of Incorporation); or
(iv) such time as the Investor (together with its affiliates) no longer holds any shares of Series Seed Preferred Stock of the Company (or shares of Common Stock issued upon conversion thereof).
7.3 Survival. Notwithstanding the foregoing, Section 8 (Confidentiality) and Section 10 (Governing Law; Dispute Resolution) shall survive the termination or expiration of this Side Letter in accordance with their respective terms.
8. CONFIDENTIALITY
8.1 General Obligation. The terms and provisions of this Side Letter are confidential and shall not be disclosed by either Party to any third party without the prior written consent of the other Party, except as expressly provided in this Section 8.
8.2 Permitted Disclosures. Notwithstanding Section 8.1, either Party may disclose the terms and provisions of this Side Letter:
(i) to such Party's respective legal counsel, accountants, auditors, and professional advisors (including, with respect to the Investor, Calderwood & Harkness LLP and Morgan Tsai, VP of Legal Affairs of Cobalt Ventures LP), in each case on a need-to-know basis and subject to obligations of confidentiality no less protective than those set forth herein;
(ii) with respect to the Investor, to the Investor's general partner (Cobalt Ventures GP III, LLC), its limited partners, and its affiliates, on a need-to-know basis and subject to obligations of confidentiality no less protective than those set forth herein;
(iii) as required by applicable law, regulation, or legal process, provided that the disclosing Party shall, to the extent permitted by law, provide the other Party with prompt written notice of any such required disclosure and shall cooperate with the other Party in seeking a protective order or other appropriate remedy; or
(iv) to the extent necessary in connection with the enforcement of rights under this Side Letter or any of the Transaction Documents.
8.3 Information Received Under This Side Letter. All information received by the Investor, its Observer, or its representatives pursuant to Section 2 (Additional Information Rights) and Section 5 (Annual Data Privacy and Security Compliance Audit Right) of this Side Letter shall be treated as confidential and proprietary information of the Company and shall be subject to the confidentiality obligations set forth in this Section 8 and, to the extent applicable, the confidentiality provisions of the IRA.
9. RELATIONSHIP TO TRANSACTION DOCUMENTS
9.1 Supplemental Agreement. This Side Letter is supplemental to, and shall be read together with, the Transaction Documents. The execution and delivery of this Side Letter is a condition to the closing of the transactions contemplated by the Purchase Agreement.
9.2 Conflict. In the event of any conflict or inconsistency between the terms of this Side Letter and the terms of the Purchase Agreement, the IRA, the Voting Agreement, or the ROFR Agreement, the terms of this Side Letter shall control with respect to the Investor, but only to the extent of such conflict or inconsistency.
9.3 No Modification of Other Investors' Rights. This Side Letter shall not be construed to modify, amend, or otherwise affect the rights, obligations, or privileges of any investor other than the Investor under any of the Transaction Documents.
9.4 Preservation of Investor Rights. Nothing in this Side Letter shall be construed to diminish, limit, or waive any rights of the Investor under the Transaction Documents. All rights granted to the Investor hereunder are in addition to, and not in limitation of, any rights granted to the Investor under the Purchase Agreement, the IRA, the Voting Agreement, and the ROFR Agreement.
10. GOVERNING LAW; DISPUTE RESOLUTION
10.1 Governing Law. This Side Letter shall be governed by and construed in accordance with the internal laws of the State of Delaware, without giving effect to the principles of conflicts of law thereof that would require or permit the application of the laws of any other jurisdiction.
10.2 Dispute Resolution. Any dispute, controversy, or claim arising out of or relating to this Side Letter, or the breach, termination, or validity thereof, shall be resolved in accordance with the dispute resolution provisions set forth in Section 9 of the Purchase Agreement, which provisions are hereby incorporated by reference and shall apply mutatis mutandis to this Side Letter.
11. NOTICES
All notices, requests, demands, consents, and other communications required or permitted under this Side Letter shall be in writing and shall be delivered in accordance with the notice provisions set forth in Section 7 of the Purchase Agreement. Without limiting the foregoing, notices shall be sent to the following addresses (or to such other address as a Party may designate by written notice to the other Party in accordance with this Section 11):
If to the Company:
Meridian Diagnostics, Inc. 225 Binney Street, Suite 400 Cambridge, MA 02142
Attention: Dr. Priya Ramaswamy, Chief Executive Officer & President
Email: pramaswamy@meridiandiagnostics.com
with a copy (which shall not constitute notice) to:
Whitfield & Ames LLP 100 Federal Street, 30th Floor Boston, MA 02110
Attention: Catherine Devereaux
Email: cdevereaux@whitfieldames.com
If to the Investor:
Cobalt Ventures Fund III, LP c/o Cobalt Ventures LP 2400 Sand Hill Road, Suite 310 Menlo Park, CA 94025
Attention: Elaine Cho, Managing Partner, and Morgan Tsai, VP of Legal Affairs
Email: echo@cobaltventures.com; mtsai@cobaltventures.com
with a copy (which shall not constitute notice) to:
Calderwood & Harkness LLP 1800 Page Mill Road, Suite 200 Menlo Park, CA 94025
Attention: Kevin Ostrowski
Email: kostrowski@calderwoodharkness.com
12. AMENDMENTS AND WAIVERS
12.1 Amendments. This Side Letter may be amended, modified, or supplemented only by a written instrument executed and delivered by both the Company and the Investor. No oral agreement, course of dealing, or trade usage shall be effective to amend, modify, or supplement the terms of this Side Letter.
12.2 Waivers. No waiver of any provision of this Side Letter, or of any right or remedy hereunder, shall be effective unless set forth in a written instrument signed by the Party to be bound thereby. No waiver of any provision shall constitute a waiver of any other provision, nor shall any waiver of any provision on one occasion constitute a waiver of such provision on any future occasion. The failure or delay of either Party in exercising any right, power, or privilege under this Side Letter shall not operate as a waiver thereof.
13. ASSIGNMENT
This Side Letter and the rights and obligations hereunder may not be assigned or transferred by either Party without the prior written consent of the other Party, which consent may be granted or withheld in such Party's sole discretion; provided, however, that the Investor may, without the prior written consent of the Company, assign its rights (but not its obligations, except in connection with a transfer of shares as described below) under this Side Letter to:
(a) any affiliate of the Investor (as defined in Rule 405 under the Securities Act of 1933, as amended); or
(b) any transferee of all or substantially all of the Investor's shares of Series Seed Preferred Stock (or Common Stock issued upon conversion thereof) of the Company, provided that such transferee agrees in writing, in a form reasonably satisfactory to the Company, to be bound by the terms and conditions of this Side Letter as if such transferee were the original "Investor" hereunder.
Any attempted assignment in violation of this Section 13 shall be null and void and of no force or effect.
14. ENTIRE AGREEMENT
This Side Letter, together with the Transaction Documents (including all exhibits, schedules, and annexes thereto), constitutes the entire agreement between the Parties with respect to the subject matter hereof and supersedes all prior and contemporaneous negotiations, discussions, proposals, agreements, representations, warranties, and understandings, whether written or oral, relating to the subject matter hereof. Neither Party has relied upon any statement, representation, warranty, or agreement of the other Party except for those expressly set forth in this Side Letter and the Transaction Documents.
15. COUNTERPARTS; ELECTRONIC SIGNATURES
This Side Letter may be executed in one or more counterparts, each of which shall be deemed an original and all of which, taken together, shall constitute one and the same instrument. The exchange of executed counterparts of this Side Letter by electronic means (including by PDF transmitted via email or by electronic signature platform such as DocuSign or similar service) shall be sufficient to bind the Parties, and such electronic copies or signatures shall be deemed original signatures for all purposes and shall be admissible in any legal proceeding arising under or in connection with this Side Letter.
16. SEVERABILITY
If any provision of this Side Letter, or the application of any such provision to any person, entity, or circumstance, shall be held to be invalid, illegal, or unenforceable by a court of competent jurisdiction, the remainder of this Side Letter and the application of such provision to other persons, entities, or circumstances shall not be affected thereby, and each remaining provision of this Side Letter shall be valid and enforceable to the fullest extent permitted by applicable law. In the event that any provision is so held to be invalid, illegal, or unenforceable, the Parties shall negotiate in good faith to replace such provision with a valid, legal, and enforceable provision that, to the greatest extent possible, achieves the original intent and economic effect of the invalid, illegal, or unenforceable provision.
[Signature Page Follows]
IN WITNESS WHEREOF, the Parties have executed this Side Letter Agreement as of the date first written above.
MERIDIAN DIAGNOSTICS, INC.
By: ________
Name: Dr. Priya Ramaswamy
Title: Chief Executive Officer & President
Date: February 9, 2026
COBALT VENTURES FUND III, LP
By: Cobalt Ventures GP III, LLC, its General Partner
By: ________
Name: Elaine Cho
Title: Managing Partner
Date: February 9, 2026
[Signature Page to Side Letter Agreement]

SIDE LETTER AGREEMENT

RECITALS

MERIDIAN DIAGNOSTICS, INC.

COBALT VENTURES FUND III, LP

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Parties

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