Company: NCEL
Filing Date: 2025-06-06
Form Type: 425
Source: 0001213900-25-052102
Chunk: 0

Company: NewcelX Ltd.
Filing Date: 2025-06-06
Form: 425
Chunk 0
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Filed by NLS Pharmaceutics Ltd. pursuant to

Rule 425 under the Securities Act of 1933, as amended

Subject Company: Kadimastem Ltd.

<div align='center'>UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 6-K

Report of Foreign Private Issuer

Pursuant to Rule 13a-16 or 15d-16

under the Securities Exchange Act of 1934

For the month of June 2025

Commission file number: 001-39957

NLS PHARMACEUTICS LTD.

(Translation of registrant’s name into English)

The Circle 6

8058 Zurich, Switzerland

(Address of principal executive offices)</div>

Indicate by check mark whether the registrant files or will file annual
reports under cover of Form 20-F or Form 40-F.

<div align='center'>Form 20-F ☒ Form
40-F ☐

CONTENTS</div>

Fourth Amendment to the Merger Agreement

On June 5, 2025, NLS Pharmaceutics Ltd. (the “Company”) entered into a fourth amendment (the “Fourth Amendment”)
to the Agreement and Plan of Merger, dated November 4, 2024, and as previously amended on January 30, 2025, February 17, 2025, and on
May 5, 2025 (as so amended, the “Merger Agreement”) among the Company, Kadimastem Ltd. (“Kadimastem”) and NLS
Pharmaceutics (Israel) Ltd. (collectively, the “Parties”).

Pursuant to the terms of the Fourth Amendment, the Parties clarified the definition and calculation of “Exchange Ratio” (as
defined in the Merger Agreement) to account for the valuation of the Company and the Combined Company (as defined in the Merger Agreement)
and to reflect the initial target post-Closing fully diluted share split between the shareholders of Kadimastem and the shareholders of
the Company of 85% (Kadimastem shareholders) and 15% (Company shareholders). In addition, pursuant to the terms of the Fourth Amendment,
the Parties clarified the potential adjustments to such initial target as a result of the Closing Cash (as defined in the Merger Agreement),
the Closing Indebtedness (as defined in the Merger Agreement), the Parent Adjusted Cash