UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 OR 15(d) of The Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): June 23, 2022

RIGEL PHARMACEUTICALS, INC.

(Exact name of registrant as specified in its charter)

Delaware

(State or other jurisdiction of incorporation)

Registrant’s telephone number, including area code: (650) 624-1100

Not Applicable

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

¨ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

¨ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

¨ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

¨ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ¨

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨

On June 23, 2022, Rigel Pharmaceuticals, Inc. (the “Company”) announced that it has received a Paragraph IV Certification Notice Letter (the “Notice Letter”) from Annora Pharma Private Limited (“Annora”) advising that Annora had submitted an Abbreviated New Drug Application (“ANDA”) to the U.S. Food and Drug Administration (“FDA”) seeking authorization from the FDA to manufacture, use or sell a generic version of TAVALISSE® fostamatinib disodium tablets, Eq. 100mg base and Eq. 150mg base, (“TAVALISSE®”) in the United States.

The Notice Letter contains Paragraph IV certifications against certain of the Company’s patents related to TAVALISSE® which are listed in the FDA’s Approved Drug Products with Therapeutic Equivalence Evaluations (referred to as the “Orange Book”). The Notice Letter alleges that the patents will not be infringed by Annora’s proposed product, are invalid and/or are unenforceable. The Company intends to vigorously enforce and defend its intellectual property rights related to TAVALISSE®.

Forward-Looking Statements

This Current Report on Form 8-K contains forward-looking statements relating to, among other things, the Company’s intention to vigorously enforce its intellectual property rights. Any such statements that are not statements of historical fact may be deemed to be forward-looking statements. Words such as “potential,” “may,” “expects,” “intends” and similar expressions are intended to identify these forward-looking statements. These forward-looking statements are based on the Company’s current expectations and inherently involve significant risks and uncertainties. Actual results and the timing of events could differ materially from those anticipated in such forward looking statements as a result of these risks and uncertainties, which include, without limitation, those risks and uncertainties relating to the Company’s ability to successfully enforce its intellectual property rights and to defend its patents; the possible introduction and timing of generic competition to TAVALISSE®; the Company’s dependence on TAVALISSE®; as well as other risks detailed from time to time in the Company’s reports filed with the Securities and Exchange Commission, including its Annual Report on Form 10-K for the year ended December 31, 2021 and Quarterly Report on Form 10-Q for the quarter ended March 31, 2022. The Company does not undertake any obligation to update any forward-looking statements and expressly disclaims any obligation or undertaking to release publicly any updates or revisions to any forward-looking statements contained herein.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.