Company: ARMP
Filing Date: 2025-12-01
Form Type: 424B5
Source: 0001104659-25-117382
Chunk: 0

Company: Armata Pharmaceuticals, Inc.
Filing Date: 2025-12-01
Form: 424B5
Chunk 0
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Filed pursuant to Rule 424(b)(5)

Registration Statement No. 333-289585

Prospectus Supplement

(To Prospectus dated August 22, 2025)

<div align='center'>Up to $100,000,000 of Shares of Common Stock</div>

Armata Pharmaceuticals, Inc., a Washington corporation
(“Armata,” the “Company,” “we,” “us” or “our”), has entered into Capital on
Demand™ Sales Agreement, dated December 1, 2025 (the “Sales Agreement”) with JonesTrading Institutional Services LLC
(“Jones”), relating to the offer and sale of shares of our common stock, par value $0.01 per share, from time to time, offered
by this prospectus supplement and the accompanying base prospectus. In accordance with the terms of the Sales Agreement, under this prospectus
supplement and the accompanying base prospectus, we may offer and sell shares of our common stock having an aggregate offering price of
up to $100,000,000 from time to time subject to certain conditions, through or to Jones, acting as agent or principal.

Our common stock is traded on the New York Stock
Exchange (the “NYSE”) American under the trading symbol “ARMP.” On November 25, 2025, the last reported sale price
of our common stock on the NYSE American was $7.10.

Sales of our common stock, if any, under this
prospectus supplement may be made by any method permitted that is deemed an “at the market offering” as defined in Rule 415
under the Securities Act of 1933, as amended (the “Securities Act”). Jones is not required to sell any specific amount but
will act as our sales agent and use commercially reasonable efforts to sell on our behalf the shares of common stock requested to be sold
by us, consistent with its normal trading and sales practices, on mutually agreed terms between Jones and us. There is no arrangement
for funds to be received in escrow, trust or similar arrangement.

Jones will be entitled to compensation at a commission
rate of up to 3.0% of the gross sales price per share of common stock sold through it as sales agent pursuant to the Sales Agreement.
In connection with the sale of shares of our common stock on our behalf, Jones will be deemed to be an “underwriter” within
the meaning of the Securities Act and the compensation of Jones will be deemed to be underwriting