Company: PSTV
Filing Date: 2025-06-20
Form Type: S-1/A
Source: 0001193125-25-142935
Chunk: 7

Company: PLUS THERAPEUTICS, INC.
Filing Date: 2025-06-20
Form: S-1/A
Chunk 7
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, but not the obligation to sell to Lincoln Park under the Purchase Agreement. Any proceeds that we receive from sales of shares of our common stock to       
 Lincoln Park under the Purchase Agreement will be used for working capital and general corporate purposesa and to the extent required, for Make-Whole Repayment (as defined in the “Use of Proceeds” section). See “Use of Proceeds.”                    |

| Nasdaq symbol for our common stock | “PSTV” |

| Risk factors | This investment involves a high degree of risk. See “Risk Factors” beginning on page 4 of this prospectus for a discussion of factors you should carefully consider before deciding to invest in our securities. |

Unless otherwise noted, the number of shares of common stock to be outstanding immediately after this offering is based on 50,998,468 shares outstanding as of June 17, 2025 and excludes, as of June 17, 2025:

| • |     | 1,230,272 shares of common stock issuable upon exercise of stock options outstanding under our equity incentive 
 plans, with a weighted-average exercise price of $3.79 per share;                                               |

| • |     | 7,668 shares of common stock reserved for future issuance under our 2015 New Employee Incentive Plan; |

| • |     | 1,222,604 shares of common stock reserved for future issuance under our 2020 Stock Incentive Plan; |

| • |     | 398 and 27,792 shares of common stock issuable upon conversion of 1,014 shares of Series B Convertible Preferred 
 Stock and 938 shares of Series C Preferred Stock, respectively;                                                  |

2

| • |     | 46,170,030 shares of common stock issuable upon exercise of pre-funded or zero strike price warrants to purchase 
 common stock; and                                                                                                |

| • |     | 3,141,993 shares of common stock issuable upon the exercise of warrants to purchase common stock, with a 
 weighted-average exercise price of $1.79 per share.                                                      |

3

RISK FACTORS

Investing in our securities involves a high degree of risk. Before making an investment decision with respect to our securities, we urge you to carefully consider the risks described below and in the “Risk Factors” sections of our most recent Annual Report on Form 10-Kand Quarterly Reports on Form 10-Q,as well as our Current Reports on Form 8-K,filed with the