EX-10.5

CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY [*], HAS BEEN OMITTED BECAUSE IT IS BOTH (I) NOT MATERIAL AND (II) IS THE TYPE THAT THE REGISTRANT TREATS AS PRIVATE OR CONFIDENTIAL.

Exhibit 10.5

AMENDMENT NO. 1 TO AMENDED AND RESTATED CREDIT, SECURITY AND GUARANTY AGREEMENT

This AMENDMENT NO. 1 TO AMENDED AND RESTATED CREDIT, SECURITY AND GUARANTEE AGREEMENT (this“Agreement”)ismadeasofthis11thdayofMay,2026,byandamong RIGEL PHARMACEUTICALS, INC., a Delaware corporation (“Rigel”), as a Borrower, MIDCAP FUNDINGIVTRUST,asAgent(insuchcapacity,togetherwithitssuccessorsandassigns,“Agent”)and the financial institutions or other entities from time to time parties to the Credit Agreement referenced below, each as a Lender.

RECITALS

A.Agent,LendersandBorrowerhaveenteredintothatcertainAmendedandRestatedCredit, Security and Guaranty Agreement, dated as of May 5, 2026 (as amended, supplemented or otherwise modifiedfrom timetotimeprior tothe date hereof,the “Existing Credit Agreement” and, as the same is amendedherebyandasitmaybefurtheramended,modified,supplementedandrestatedfromtimetotime, the“CreditAgreement”),pursuanttowhichtheLendershaveagreedtomakecertainadvancesof money and to extend certain financial accommodations to Borrower in the amounts and manner set forth in the Credit Agreement.

B.Borrower has notified agent that it wishes to enter into that certain License Agreement, dated as of May 11, 2026, by and among Rigel, Arvinas, Inc., Arvinas Operations, Inc., Arvinas Estrogen Receptor, Inc., and Pfizer Inc. [*] (the “Arvinas License Agreement”),andthattheenteringintooftheArvinasLicenseAgreementandthepaymentoftheArvinas Payments (as defined in the Credit Agreement, as amended hereby) would not be permitted under the Existing Credit Agreement;

C.Borrowerhasrequested,andAgentandLendershaveagreed,topermit(a)(i)theBorrower toenterintotheArvinasLicenseAgreementand(ii)thepaymentbytheBorroweroftheArvinasPayments required thereunder and (b) to amend certain provisions of the Existing Credit Agreement in accordance with the terms and subject to the conditions set forth herein:

AGREEMENT

NOW, THEREFORE, in consideration of the foregoing, the terms and conditions set forth in this Agreement, and other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, Agent, Lenders and Borrower hereby agree as follows:

1.Recitals.ThisAgreementshallconstituteaFinancingDocumentandtheRecitalsandeach referencetotheCreditAgreement,unlessotherwiseexpresslynoted,willbedeemedtoreferencetheCredit Agreement as amended hereby.Capitalized terms used but not otherwise defined herein shall have the meaningsascribedtothemintheCredit Agreement (includingthosecapitalizedtermsusedinthe Recitals hereto).

2.AmendmentstoExistingCreditAgreement.Subjecttothetermsandconditionsofthis Agreement, including, without limitation, the conditions to effectiveness set forth in Section 4below, the Existing Credit Agreement is hereby amended as follows:

(a)Section 1.1 of the Existing Credit Agreement is hereby amended by adding thefollowing new defined term in the appropriate alphabetical order therein:

“ArvinasLicenseAgreement”meansthatcertainLicenseAgreement,datedas ofMay11,2026,byandamongRigel,Arvinas,Inc.,ArvinasOperations,Inc.,ArvinasEstrogenReceptor, Inc.,andPfizer,Inc.[*],asamended,supplemented or otherwise modified from time to time in accordance with the terms thereof and the terms of this Agreement.

“Arvinas Payment” means any payment required to be made by or on behalf of RigeloranyofitsSubsidiariesonorfollowingtheFirstAmendmentEffectiveDatepursuantto[*] the Arvinas LicenseAgreement.

(b)“FirstAmendment”meansthatcertainAmendmentNo.1toAmendedand Restated Credit Agreement, dated as of May 11, 2026, among Borrower, Agent and Lenders.

(c)“FirstAmendmentEffectiveDate”meansMay11,2026.

(d)“SpecifiedEventofDefault”meansanEventofDefaultsetforthinSection 10.1(a)(i), 10.1(a)(ii) *solely with respect to a default under Article 6), 10.1(e), 10.1(f) or 10.1(m).

(e)Thedefinitionof“MaterialContracts”inSection1.1oftheExistingCredit Agreement is hereby amended in its entirety to read as follows:

“MaterialContracts”means(a)theagreementslistedonSchedule3.17,including theGrifolsLicenseAgreement,theFormaLicenseAgreementandtheArvinasLicenseAgreement,and(b) any other agreement or contract that Rigel has filed with the SEC as a material agreement, including pursuant to Item 601(b)(10) of Regulation S-K, and (c) each agreement or contract to which such Credit Party or its Subsidiaries is a party the termination of which would reasonably be expected to result in a Material Adverse Effect.

(f)The definition of “Permitted Investments” in Section 1.1 of the Existing Credit Agreement is hereby by amended by:

(i)deletingtheword“and”fromtheendof clause(q);

(ii)renumberingtheexistingclause(r)asclause(s);and

(iii)adding the following new clause (r) in the appropropriate alphabetical order therein:

“(r) the Acquisition constituting the entering into of the Arvinas License Agreement and the Investments made in connection with the entering into Arvinas LicenseAgreement(includingthepaymentofallupfrontconsiderationinconnection therewith); and”

(g)The definition of “Permitted Contingent Obligations” in Section 1.1 of the ExistingCreditAgreementisherebyamendedbydeletingtheexistingclause(i)initsentiretyandreplacing it with the following:

“(i)the obligation of Rigel to make any Arvinas Payment following the first Amendment Effective Date, on and subject to the terms of the Arvinas License Agreement; provided that

(x) before and after giving effect to such payment, no Specified Event of Default has occurred and is continuing,and(y)BorrowerisincompliancewiththecovenantssetforthinSection6onaproformabasis after giving effect to such payment;”.

3.Representations and Warranties; Reaffirmation of Security Interest.Borrower hereby(a)confirmsthatalloftherepresentationsandwarrantiessetforthintheCreditAgreementaretrue and correct in all material respects (without duplication of any materiality qualifier in the text of such representationorwarranty)withrespecttoBorrowerasofthedatehereofexcepttotheextentthatanysuch representation or warrantyrelates to a specific date in which case such representation or warranty shall be true and correct as of such earlier date, and (b) covenants to perform its respective obligations under the CreditAgreement.EachBorrowerconfirmsandagreesthatallsecurityinterestsandLiensgrantedtoAgent continueinfullforceandeffect,andallCollateralremainsfreeandclearofanyLiens,otherthanPermitted Liens.Nothing herein is intended to impair or limit the validity, priority or extent of Agent’s security interestsinandLiensontheCollateral.BorroweracknowledgesandagreesthattheCreditAgreement,the other Financing Documents and this Agreement constitute the legal, valid and binding obligation of Borrower, and are enforceable against Borrower in accordance with its terms, except as the enforceability thereof may be limited by bankruptcy, insolvency or other similar laws relating to the enforcement of creditors’ rights generally and by general equitable principles.

4.Conditions to Effectiveness.This Agreement shall become effective as of the date on which each of the following conditions has been satisfied, as determined by Agent in its sole discretion:

(a)Agent shall have received (including by way of electronic transmission) a duly authorized, executed and delivered counterpart of the signature page to this Amendment from Borrower, Agent and the Lenders;

(b)Agent shall have received (including by way of electronic transmission) a dulyauthorized and fully executed copy of the Arvinas License Agreement;

(c)all representations and warranties of Borrower contained herein shall be true and correct in all material respects (without duplication of any materiality qualifier in the text of such representation or warranty) as of the date hereof except to the extent that any such representation or warranty relates to a specific date in which case such representation or warranty shall be true and correct as of such earlier date (and such parties’ delivery of their respective signatures hereto shall be deemed to be its certification thereof);

(d)prior to and after giving effect to the agreements set forth herein, no Default orEvent of Default shall exist under any of the Financing Documents; and

(e)Agent shall have received such other documents, certificates, and information as Agent may reasonably request in connection with this Agreement.

5.Conditions Subsequent. Prior to the occurrence of the Effective Date set forth in the Arvinas License Agreement, Agent shall have received a certificate from a Responsible Officer, in form andsubstancesatisfactorytoAgent,demonstratingthatCreditPartiesareincompliancewiththecovenants set forth in Article 6 of the Credit Agreement on a pro forma basis after giving effect to the making of all paymentsrequiredtobemadebyBorrowers,includingthepaymentof[*], upon consummating the transactions contemplated under the Arvinas License Agreement.

Release.In consideration of the agreements of Agent and Lenders contained herein and for other good and valuable consideration, the receipt and sufficiency of which is hereby acknowledged, Borrower, voluntarily, knowingly, unconditionally and irrevocably, with specific and express intent, for and on behalf of itself and all of its respective parents, subsidiaries, affiliates, members, managers, predecessors, successors, and assigns, and each of its respective current and former directors, officers, shareholders,agents,andemployees,andeachofitsrespectivepredecessors,successors,heirs,andassigns

(individually and collectively, the “Releasing Parties”) does hereby fully and completely release, acquit and forever discharge each of Agent, Lenders, and each their respective parents, subsidiaries, affiliates, members, managers, shareholders, directors, officers and employees, and each of their respective predecessors,successors,heirs,andassigns(individuallyandcollectively,the“ReleasedParties”),ofand from any and all actions, causes of action, suits, debts, disputes, damages, claims, obligations, liabilities, costs, expenses and demands of any kind whatsoever, at law or in equity, whether matured or unmatured, liquidatedor unliquidated,vested orcontingent,choate orinchoate,knownor unknownthattheReleasing Parties (or any of them) has against the Released Parties or any of them (whether directly or indirectly), based in whole or in part on facts, whether or not now known, existing on or before the date hereof, that relate to, arise out of or otherwise are in connection with: (i) any or all of the Financing Documents or transactionscontemplatedtherebyoranyactionsoromissionsinconnectiontherewithor(ii)anyaspectof the dealings or relationships between or among any Borrower, on the one hand, and any or all of the Released Parties, on the other hand, relating to any or all of the documents, transactions, actions or omissions referenced in clause (i) hereof, in each case, based in whole or in part on facts, whether or not nowknown,existingbeforethedatehereof.Borroweracknowledgesthattheforegoingreleaseisamaterial inducement to Agent’s and each Lender’s decision to enter into this Agreement and agree to the modifications contemplated hereunder, and has been relied upon by Agent and Lenders in connection therewith.

6.No Waiver or Novation.The execution, delivery and effectiveness of this Agreement shallnot,exceptasexpresslyprovidedinthisAgreement,operateasawaiverofanyright,powerorremedy of Agent, nor constitute a waiver of any provision of the Credit Agreement, the Financing Documents or any other documents, instruments and agreements executed or delivered in connection with any of the foregoing.Nothinghereinisintendedor shall beconstruedasawaiver of anyexistingDefaultsor Events of Default under the Credit Agreement or the other Financing Documents or any of Agent’s rights and remedies in respect of such Defaults or Events of Default.This Agreement (together with any other documentexecutedinconnectionherewith)isnotintendedtobe,norshallitbeconstruedas,anovationof the Credit Agreement.

7.Affirmation.Except as specifically amended pursuant to the terms hereof, Borrower hereby acknowledges and agrees that the Credit Agreement and all other Financing Documents (and all covenants, terms, conditions and agreements therein) shall remain in full force and effect, and are hereby ratified and confirmed in all respects by Borrower.Borrower covenants and agrees to comply with all of the terms, covenants and conditions of the Credit Agreement and the Financing Documents, notwithstanding any prior course of conduct, waivers, releases or other actions or inactions on Agent’s or any Lender’s part which might otherwise constitute or be construed as a waiver of or amendment to such terms, covenants and conditions.

8.Miscellaneous.

(a)Reference to the Effect on the Credit Agreement.Upon the effectiveness of this Agreement, eachreferenceinthe CreditAgreement to“this Agreement,”“hereunder,”“hereof,”“herein,” or words of similar import shall mean and be a reference to the Credit Agreement, as amended by this Agreement.Except as specifically amended above, the Credit Agreement, and all other Financing Documents (and all covenants, terms, conditions and agreements therein), shall remain in full force and effect, and are hereby ratified and confirmed in all respects by Borrower.

(b)GOVERNING LAW.THIS AGREEMENT AND ALL DISPUTES AND OTHER MATTERS RELATING HERETO OR THERETO OR ARISING THEREFROM (WHETHER SOUNDING IN CONTRACT LAW, TORT LAW OR OTHERWISE), SHALL BE GOVERNED BY, AND SHALL BE CONSTRUED AND ENFORCED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK, WITHOUT REGARD TO CONFLICTS OF LAWS PRINCIPLES (OTHERTHAN SECTION 5-1401 OF THE GENERAL OBLIGATIONS LAW).

(c)WAIVER OF JURY TRIAL.BORROWER, AGENT AND THE LENDERS PARTYHERETOHEREBYIRREVOCABLYWAIVESANYANDALLRIGHTTOTRIALBYJURY IN ANY LEGAL ACTION OR PROCEEDING ARISING OUT OF OR RELATING TO THIS AGREEMENT OR THE TRANSACTIONS CONTEMPLATED HEREBY AND AGREES THAT ANY SUCH ACTION OR PROCEEDING SHALL BE TRIED BEFORE A COURT AND NOT BEFORE A JURY.BORROWER,AGENTANDEACHLENDERACKNOWLEDGESTHATTHISWAIVERISA MATERIAL INDUCEMENT TO ENTER INTO A BUSINESS RELATIONSHIP, THAT EACH HAS RELIED ON THE WAIVER IN ENTERING INTO THIS AGREEMENT, AND THAT EACH WILL CONTINUE TO RELY ON THIS WAIVER IN THEIR RELATED FUTURE DEALINGS. BORROWER,AGENTANDEACHLENDERWARRANTSANDREPRESENTSTHATITHASHAD THEOPPORTUNITYOFREVIEWINGTHISJURYWAIVERWITHLEGALCOUNSEL,ANDTHAT IT KNOWINGLY AND VOLUNTARILY WAIVES ITS JURY TRIAL RIGHTS.

(d)Incorporation of Credit Agreement Provisions.The provisions contained in Article 13(Choice of law; venue and jury trial waiver; California waivers, indemnification) of the Credit Agreementareincorporatedhereinbyreferencetothesameextentasifreproducedhereinintheirentirety.

(e)Headings.Section headings in this Agreement are included for convenience of reference only and shall not constitute a part of this Agreement for any other purpose.

(f)Counterparts.ThisAgreementmaybesignedinanynumberofcounterparts,each ofwhichshallbedeemedanoriginalandallofwhichwhentakentogethershallconstituteoneandthesame instrument.The words “execution,” “signed,” “signature,” and words of like import in this Amendment shall be deemed to include electronic signatures or electronic records, each of which shall be of the same legal effect, validity or enforceability as a manually executed signature or the use of a paper-based recordkeepingsystem,asthecasemaybe,totheextentandasprovidedforinanyapplicablelaw,including the Federal Electronic Signatures in Global and National Commerce Act, the New York State Electronic Signatures and Records Act, or any other similar statelaws based on the Uniform Electronic Transactions Act. Delivery of an executed counterpart of this Agreement by facsimile or by electronic mail delivery of anelectronicversion(e.g.,.pdfor.tiffile)ofanexecutedsignaturepageshallbeeffectiveasdeliveryofan original executed counterpart hereof and shall bind the parties hereto.

(g)EntireAgreement.This Agreement constitutes the entire agreement and understanding among the parties hereto and supersedes any and all prior agreements and understandings, oral or written, relating to the subject matter hereof.

(h)Severability.IncaseanyprovisionoforobligationunderthisAgreementshallbe invalid, illegal or unenforceable in any applicable jurisdiction, the validity, legality and enforceability of the remaining provisions or obligations, or of such provision or obligation in any other jurisdiction, shall not in any way be affected or impaired thereby.

(i)Successors/Assigns.This Agreement shall bind, and the rights hereunder shall inure to, the respective successors and assigns of the parties hereto, subject to the provisions of the Credit Agreement and the other Financing Documents.

[SIGNATURESAPPEARONFOLLOWINGPAGES]

INWITNESSWHEREOF,intendingtobelegallybound,theundersignedhaveexecutedthis Agreement as of the day and year first hereinabove set forth.

AGENT: MIDCAPFUNDINGIVTRUST,

By: ApolloCapitalManagement,L.P., its investment manager

By: ApolloCapitalManagementGP,LLC, its general partner

By:/s/ Maurice Amsellem

Name: Maurice Amsellem

Title:AuthorizedSignatory

[*]

LENDERS: MIDCAPFUNDINGIVTRUST

By: ApolloCapitalManagement,L.P., its investment manager

By: ApolloCapitalManagementGP,LLC, its general partner

By:/s/ Maurice Amsellem

Name: Maurice Amsellem

Title:AuthorizedSignatory

BORROWER: RIGEL PHARMACEUTICALS, INC.

By: /s/ Dean Schorno

Name:Dean Schorno

Title:EVP,ChiefFinancialOfficer

FILING DETAILS