Amendment to Quarterly Report (Form 10-Q/A)

Puma Biotechnology, Inc. (the "Company") is filing this Amendment No. 1 on Form 10-Q/A (this "Amendment") to its Quarterly Report on Form 10-Q for the quarterly period ended March 31, 2025, which was originally filed with the Securities and Exchange Commission on May 8, 2025 (the "Original Filing"), to revise Part II "Item 5. Other Information" of the Original Filing to add a Rule 10b5-1 trading arrangement entered into by Troy Wilson, a member of the Company's board of directors, adopted on March 12, 2025, which was inadvertently omitted from the disclosure included in the Original Filing.

In addition, as required by Rule 12b-15 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), new certifications by the Company's principal executive officer and principal financial officer are filed herewith as exhibits to this Amendment, under Item 6 hereof, pursuant to Rule 13a-14(a) or 15d-14(a) of the Exchange Act. Because no financial statements have been included in this Amendment and this Amendment does not contain or amend any disclosure with respect to Items 307 and 308 of Regulation S-K, paragraphs 3, 4 and 5 of the certifications have been omitted. The Company is also not including new certifications under 18 U.S.C. 1350 as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, as no financial statements are being filed with this Amendment.

This Amendment does not reflect events occurring after the filing of the Original Filing or modify or update those disclosures affected by subsequent events. Except for the items described above or contained in this Amendment, this Amendment speaks as of the original filing date of the Original Filing, and does not modify, amend or update any other item or disclosures in the Original Filing.