Northwest Biotherapeutics delays 2025 10-K filing

Northwest Biotherapeutics notified the SEC it cannot timely file its Annual Report on Form 10-K for the fiscal year ended December 31, 2025.

Rhea-AI Filing Summary

Northwest Biotherapeutics notified the SEC it cannot timely file its Annual Report on Form 10-K for the fiscal year ended December 31, 2025. The company cites complex accounting issues from its acquisition of Advent BioServices, including differences between UK GAAP and US GAAP, and says it will file the 2025 Annual Report as soon as reasonably practicable.

Insights

Accounting Policy Specialist

Late 10-K driven by cross-jurisdictional accounting differences.

The filing states the delay stems from complex accounting matters tied to the Advent BioServices acquisition, specifically reconciling UK GAAP with US GAAP. This work typically requires additional disclosure mapping and audit procedures.

Timing depends on completion of the independent auditor's interim review and any adjustments that arise; subsequent filings will reflect those outcomes.

Corporate Governance Advisor

Procedural notice preserves compliance while the company finalizes audited results.

Using Rule 12b-25 lets the company assert it cannot file without unreasonable effort or expense and signals intent to file within the permitted extension period. The company also included a forward-looking caution on timing tied to auditor reviews.

Watch for a subsequent filing that contains audited financials and any restatements or expanded disclosures tied to the acquisition.

Key Figures

Fiscal period end: December 31, 2025 Form 12b-25 signature date: March 31, 2026 Extension window (referenced): fifteen calendar day extension +1 more

4 metrics

Fiscal period end December 31, 2025 Period covered by the delayed Form 10-K

Form 12b-25 signature date March 31, 2026 Date the notification was signed by CEO Linda F. Powers

Extension window (referenced) fifteen calendar day extension Permitted post-due date extension for annual reports under Rule 12b-25(b)

Contact telephone area code 240 Registrant contact phone area code listed in the notice

Key Terms

Rule 12b-25, UK GAAP, US GAAP, interim review

4 terms

Rule 12b-25 regulatory

"The Company has determined that it is unable, without unreasonable effort or expense, to file its Annual Report"

Rule 12b-25 is an SEC filing provision that lets a company notify regulators and the public that it cannot file a required periodic report (like a quarterly or annual report) on time and explains the reason for the delay. For investors, the notice is a formal heads-up that financial information will arrive late—similar to a company calling to say it will be late turning in homework—so it signals increased uncertainty and may affect trading and risk assessments until the filing is available.

UK GAAP financial

"complex issues related to the Company’s acquisition of Advent BioServices were encountered, including due to differences in UK GAAP"

US GAAP financial

"including due to differences in UK GAAP and US GAAP"

U.S. GAAP is the set of official accounting rules and standards companies in the United States use to record and report their financial results. Like a common recipe book for financial statements, it makes company reports consistent and easier to compare, so investors can better judge profitability, risk and trends when deciding to buy, hold or sell shares.

interim review financial

"timing and completion of the necessary interim review and audits by the Company’s independent registered public accounting firm"

An interim review is a limited, formal check of a company’s financial information for a period shorter than a year—typically a quarter—carried out between full annual audits. It provides accountants’ limited assurance that the interim statements are free of material misstatement, like a spot-check instead of a full inspection, and matters to investors because it gives independent, but less comprehensive, confirmation about the reliability of short-term results and disclosures.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

Why did NWBO file a Form 12b-25 for its 2025 10-K?

The company says it cannot complete the 2025 Form 10-K without unreasonable effort due to acquisition accounting complexity. Management cited differences between UK GAAP and US GAAP from the Advent BioServices acquisition requiring additional review and auditor procedures.

When does NWBO expect to file the delayed 2025 Annual Report?

NWBO states it will file the 2025 Annual Report as soon as reasonably practicable. The filing links completion to the company’s independent auditor completing required interim review and audit procedures before the report can be finalized.

Does the Rule 12b-25 notice change NWBO's reporting obligations?

No. The notice requests relief under Rule 12b-25 and preserves the company’s attempt to comply with SEC timelines. It signals an extension period is being sought while additional accounting and audit work is completed.

What specific accounting issue caused the delay for NWBO?

The company attributes the delay to reconciling accounting differences arising from its acquisition of Advent BioServices. It specifically references challenges converting or aligning UK GAAP items with US GAAP for the annual report.

Will NWBO provide updates about the 10-K filing timing?

The company’s statement ties filing timing to the completion of the independent registered public accounting firm’s review. NWBO included forward-looking language and disclaims obligation to update except as required by law.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Accepted by SEC EDGAR 03/31/2026 - 05:04 PM Learn about SEC filing dates

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 12b-25

NOTIFICATION OF LATE FILING

(Check one):	x  Form 10-K ¨ Form 20-F ¨ Form 11-K ¨ Form 10-Q  ¨ Form 10-D ¨ Form N-CEN ¨ Form N-CSR
	For Period Ended: December 31, 2025
	¨ Transition Report on Form 10-K
	¨ Transition Report on Form 20-F
	¨ Transition Report on Form 11-K
	¨ Transition Report on Form 10-Q
	For the Transition Period Ended: __________
Nothing in this form shall be construed to imply that the Commission has verified any information contained herein.

If the notification relates to a portion of the filing checked above, identify the Item(s) to which the notification relates:

PART I - REGISTRANT INFORMATION

Northwest Biotherapeutics, Inc.

Full Name of Registrant

N/A

Former Name if Applicable

4800 Montgomery Lane, Suite 800

Address of Principal Executive Office (Street and Number)

Bethesda, MD 20814

City, State and Zip Code

PART II - RULES 12b-25(b) AND (c)

If the subject report could not be filed without unreasonable effort or expense and the registrant seeks relief pursuant to Rule 12b-25(b), the following should be completed. (Check box if appropriate)

x	(a)	The reason described in reasonable detail in Part III of this form could not be eliminated without unreasonable effort or expense;
	(b)	The subject annual report, semi-annual report, transition report on Form 10-K, Form 20-F, Form 11-K, Form N-CEN or Form N-CSR, or portion thereof, will be filed on or before the fifteenth calendar day following the prescribed due date; or the subject quarterly report or transition report on Form 10-Q or subject distribution report on Form 10-D, or portion thereof, will be filed on or before the fifth calendar day following the prescribed due date; and
	(c)	The accountant’s statement or other exhibit required by Rule 12b-25(c) has been attached if applicable.

PART III - NARRATIVE

State below in reasonable detail why Forms 10-K, 20-F, 11-K, 10-Q, 10-D, N-CEN, N-CSR, or the transition report or portion thereof, could not be filed within the prescribed time period.

The Company has determined that it is unable, without unreasonable effort or expense, to file its Annual Report on Form 10-K for the fiscal year ended December 31, 2025 (the “2025 Annual Report”) within the time period prescribed. During the final stages of the 10-K preparation process, complex issues related to the Company’s acquisition of Advent BioServices were encountered, including due to differences in UK GAAP and US GAAP.

The Company is working to file the 2025 Annual Report as soon as is reasonably practicable.

 Cautionary Note Regarding Forward-Looking Statements

This Form 12b-25 contains forward-looking statements, which are statements that relate to the future and are, by their nature, uncertain. Words such as “expect,” “will,” and variations of such words and similar future or conditional expressions are intended to identify forward-looking statements. These forward-looking statements include, but are not limited to, statements regarding the beliefs and expectations of the Company’s management relating to the timing of the filing of the 2025 Annual Report. These forward-looking statements are not guarantees of future results or outcomes and are subject to a number of risks and uncertainties, many of which are difficult to predict and beyond the Company’s control. Important factors that may cause actual results or outcomes to differ materially from those in the forward-looking statements include the timing and completion of the necessary interim review and audits by the Company’s independent registered public accounting firm. We disclaim and do not undertake any obligation to update or revise any forward-looking statement in this report, except as required by applicable law or regulation.

PART IV - OTHER INFORMATION

(1) Name and telephone number of person to contact in regard to this notification.

Linda F. Powers		240		497-9024
(Name)		(Area Code)		(Telephone Number)

(2) Have all other periodic reports required under Section 13 or 15(d) of the Securities Exchange Act of 1934 or Section 30 of the Investment Company Act of 1940 during the preceding 12 months or for such shorter period that the registrant was required to file such report(s) been filed? If answer is no, identify report(s).

Yes x No ¨

(3) Is it anticipated that any significant change in results of operations from the corresponding period for the last fiscal year will be reflected by the earnings statements to be included in the subject report or portion thereof?

Yes ¨ No x

If so, attach an explanation of the anticipated change, both narratively and quantitatively, and, if appropriate, state the reasons why a reasonable estimate of the results cannot be made.

Northwest Biotherapeutics, Inc.

(Name of Registrant as Specified in Charter)

has caused this notification to be signed on its behalf by the undersigned hereunto duly authorized.

			By:	/s/ Linda F. Powers
Date:	March 31, 2026			Chief Executive Officer and Chairman