Company: CYTK
Filing Date: 2025-09-08
Form Type: 8-K/A
Source: 0000950170-25-113599
Chunk: 1

Company: CYTOKINETICS INC
Filing Date: 2025-09-08
Form: 8-K/A
Chunk 1
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 period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.☐

<div align='center'>Explanatory Note</div>

On August 31, 2025, Cytokinetics, Incorporated announced that additional data related to aficamten were presented at the European Society of Cardiology Congress 2025 in Madrid, Spain, including a pre-specified analysis of the effect of aficamten on cardiac structure and function from MAPLE-HCM (Metoprolol vs Aficamten in Patients with LVOT Obstruction on Exercise Capacity in HCM), which was simultaneously published in the Journal of the American College of Cardiology, as well as a Late Breaking Clinical Science presentation related to the incidence and impact of atrial fibrillation (AF) associated with aficamten, which was simultaneously published in Heart Rhythm. The full text of the press release issued in connection with this announcement is furnished as Exhibit 99.1 to this Current Report on Form 8-K.

This Current Report on Form 8-K/A is being filed because the original Form 8-K filed on September 2, 2025 was missing a hyperlink to the press release that is furnished as Exhibit 99.1 to this Current Report on Form 8-K/A.

99.1Press Release dated August 31, 2025.

104 The cover page of this report has been formatted in Inline XBRL

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.

| Date: | September 8, 2025 | By: | CYTOKINETICS, INCORPORATED              
 /s/ John Faurescu                       |
|:------|:------------------|:----|:----------------------------------------|
|       |                   |     | SVP, Deputy General Counsel & Secretary |