MoonLake (MLTX) holder BVF sells shares but keeps 22.3% stake

Rhea-AI Filing Summary

MoonLake Immunotherapeutics’ major shareholder group BVF and affiliates report owning 16,001,284 Class A ordinary shares, or about 22.3% of the 71,727,875 shares outstanding as of February 1, 2026. The holdings are spread across several BVF funds and a managed account.

On March 31, 2026, BVF sold 1,932,354 shares at $16.79 per share, BVF II sold 1,569,116 shares at $16.79, and Biotechnology Value Trading Fund OS sold 248,530 shares at $16.79. Despite these sales, the BVF complex remains a large beneficial owner with shared voting and dispositive power across its entities.

Key Figures

BVF shares: 8,302,735 shares BVF II shares: 6,599,722 shares Trading Fund OS shares: 1,039,238 shares +5 more

8 metrics

BVF shares 8,302,735 shares Beneficially owned by Biotechnology Value Fund, L.P.; about 11.6% of class

BVF II shares 6,599,722 shares Beneficially owned by Biotechnology Value Fund II; about 9.2% of class

Trading Fund OS shares 1,039,238 shares Beneficially owned by Biotechnology Value Trading Fund OS; about 1.4% of class

BVF complex aggregate stake 16,001,284 shares Beneficially owned in aggregate by BVF, BVF II, Trading Fund OS and managed account; about 22.3%

Shares outstanding 71,727,875 shares MoonLake Class A ordinary shares outstanding as of February 1, 2026

March 31, 2026 BVF sale 1,932,354 shares at $16.79/share Shares sold by BVF on March 31, 2026

March 31, 2026 BVF II sale 1,569,116 shares at $16.79/share Shares sold by BVF II on March 31, 2026

March 31, 2026 Trading Fund OS sale 248,530 shares at $16.79/share Shares sold by Biotechnology Value Trading Fund OS on March 31, 2026

Key Terms

beneficially owned, shared dispositive power, shared voting power, managed account, +2 more

6 terms

beneficially owned financial

"As of the date hereof, (i) BVF beneficially owned 8,302,735 Shares"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

shared dispositive power financial

"Shared Dispositive Power 8,302,735.00"

shared voting power financial

"Shared Voting Power 16,001,284.00"

Shared voting power occurs when two or more parties jointly have the right to vote or decide how a block of company shares is cast, like co-owners who must agree before moving a piece of furniture. Investors care because who controls voting rights affects board elections, major corporate decisions and takeover outcomes, and shared control can alter regulatory disclosures and the practical influence any holder has over a company’s direction and value.

managed account financial

"59,589 Shares were held in the Partners Managed Account"

aggregate percentage of Shares financial

"The aggregate percentage of Shares reported owned by each person named herein is based on 71,727,875 Shares outstanding"

Schedule 13D regulatory

"If the filing person has previously filed a statement on Schedule 13G to report the acquisition"

A Schedule 13D is a legal document that investors file with regulators when they buy a large enough stake in a company to potentially influence its management or decisions. It provides details about the investor’s intention, ownership stake, and plans, helping other investors understand who is gaining control and what their motives might be.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 5)

MoonLake Immunotherapeutics

(Name of Issuer)

Class A ordinary share, par value $0.0001 per share

(Title of Class of Securities)

61559X104

(CUSIP Number)

JAMES KRATKY
BVF PARTNERS L.P., 44 Montgomery St., 40th Floor
San Francisco, CA, 94104
415-525-8830

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

03/31/2026

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.

The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

schemaVersion:

SCHEDULE 13D

CUSIP Number(s): 61559X104

1

Name of reporting person

BIOTECHNOLOGY VALUE FUND L P

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

WC

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 8,302,735.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 8,302,735.00

11

Aggregate amount beneficially owned by each reporting person

8,302,735.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

11.6 %

14

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13D

CUSIP Number(s): 61559X104

1

Name of reporting person

BVF I GP LLC

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 8,302,735.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 8,302,735.00

11

Aggregate amount beneficially owned by each reporting person

8,302,735.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

11.6 %

14

Type of Reporting Person (See Instructions)

OO

SCHEDULE 13D

CUSIP Number(s): 61559X104

1

Name of reporting person

BIOTECHNOLOGY VALUE FUND II LP

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

WC

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 6,599,722.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 6,599,722.00

11

Aggregate amount beneficially owned by each reporting person

6,599,722.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

9.2 %

14

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13D

CUSIP Number(s): 61559X104

1

Name of reporting person

BVF II GP LLC

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 6,599,722.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 6,599,722.00

11

Aggregate amount beneficially owned by each reporting person

6,599,722.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

9.2 %

14

Type of Reporting Person (See Instructions)

OO

SCHEDULE 13D

CUSIP Number(s): 61559X104

1

Name of reporting person

Biotechnology Value Trading Fund OS LP

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

WC

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

CAYMAN ISLANDS

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 1,039,238.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 1,039,238.00

11

Aggregate amount beneficially owned by each reporting person

1,039,238.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

1.4 %

14

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13D

CUSIP Number(s): 61559X104

1

Name of reporting person

BVF Partners OS Ltd.

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

CAYMAN ISLANDS

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 1,039,238.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 1,039,238.00

11

Aggregate amount beneficially owned by each reporting person

1,039,238.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

1.4 %

14

Type of Reporting Person (See Instructions)

CO

SCHEDULE 13D

CUSIP Number(s): 61559X104

1

Name of reporting person

BVF GP HOLDINGS LLC

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 14,902,457.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 14,902,457.00

11

Aggregate amount beneficially owned by each reporting person

14,902,457.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

20.8 %

14

Type of Reporting Person (See Instructions)

OO

SCHEDULE 13D

CUSIP Number(s): 61559X104

1

Name of reporting person

BVF PARTNERS L P/IL

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 16,001,284.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 16,001,284.00

11

Aggregate amount beneficially owned by each reporting person

16,001,284.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

22.3 %

14

Type of Reporting Person (See Instructions)

IA, PN

SCHEDULE 13D

CUSIP Number(s): 61559X104

1

Name of reporting person

BVF INC/IL

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 16,001,284.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 16,001,284.00

11

Aggregate amount beneficially owned by each reporting person

16,001,284.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

22.3 %

14

Type of Reporting Person (See Instructions)

CO

SCHEDULE 13D

CUSIP Number(s): 61559X104

1

Name of reporting person

LAMPERT MARK N

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 16,001,284.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 16,001,284.00

11

Aggregate amount beneficially owned by each reporting person

16,001,284.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

22.3 %

14

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13D

CUSIP Number(s): 61559X104

1

Name of reporting person

Loy Spike

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

OO

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 18,985.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 18,985.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

18,985.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

0.03 %

14

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13D

Item 1.	Security and Issuer
(a)	Title of Class of Securities: Class A ordinary share, par value $0.0001 per share
(b)	Name of Issuer: MoonLake Immunotherapeutics
(c)	Address of Issuer's Principal Executive Offices: DORFSTRASSE 29, ZUG, SWITZERLAND , 6300.
Item 3.	Source and Amount of Funds or Other Consideration
	Item 3 is hereby amended and restated to read as follows: The Shares beneficially owned by BVF, BVF2 and Trading Fund OS and held in the Partners Managed Account were purchased with working capital. The aggregate cost basis of the 8,302,735 Shares directly beneficially owned by BVF is approximately $27,709,362, including brokerage commissions. The aggregate cost basis of the 6,599,722 Shares directly beneficially owned by BVF2 is approximately $21,077,776, including brokerage commissions. The aggregate cost basis of the 1,039,238 Shares directly beneficially owned by Trading Fund OS is approximately $3,277,670, including brokerage commissions. The aggregate cost basis of the 59,589 Shares held in the Partners Managed Account is approximately $595,890, including brokerage commissions. The Shares beneficially owned by Mr. Loy were awarded to him by the Issuer in connection with his service as a director.
Item 5.	Interest in Securities of the Issuer
(a)	Item 5(a) is hereby amended and restated to read as follows: The aggregate percentage of Shares reported owned by each person named herein is based on 71,727,875 Shares outstanding as of February1, 2026, which is the total number of Shares outstanding as reported in the Issuer's Annual Report on Form 10-K filed with the Securities and Exchange Commission on February 25, 2026. As of the date hereof, (i) BVF beneficially owned 8,302,735 Shares, representing percentage ownership of approximately 11.6% of the Shares outstanding, (ii) BVF2 beneficially owned 6,599,722 Shares, representing percentage ownership of approximately 9.2% of the Shares outstanding, (iii) Trading Fund OS beneficially owned 1,039,238 Shares, representing percentage ownership of approximately 1.4% of the Shares outstanding, and (iv) 59,589 Shares were held in the Partners Managed Account, representing percentage ownership of less than 1% of the Shares outstanding. BVF GP, as the general partner of BVF, may be deemed to beneficially own the 8,302,735 Shares beneficially owned by BVF, representing percentage ownership of approximately 11.6% of the Shares outstanding. BVF2 GP, as the general partner of BVF2, may be deemed to beneficially own the 6,599,722 Shares beneficially owned by BVF2, representing percentage ownership of approximately 9.2% of the Shares outstanding. Partners OS, as the general partner of Trading Fund OS, may be deemed to beneficially own the 1,039,238 Shares beneficially owned by Trading Fund OS, representing percentage ownership of approximately 1.4% of the Shares outstanding. BVF GPH, as the sole member of each of BVF GP and BVF2 GP, may be deemed to beneficially own the 14,902,457 Shares beneficially owned in the aggregate by BVF and BVF2, representing percentage ownership of approximately 20.8% of the Shares outstanding. Partners, as the investment manager of BVF, BVF2, Trading Fund OS and the Partners Managed Account and the sole member of Partners OS, may be deemed to beneficially own the 16,001,284 Shares beneficially owned in the aggregate by BVF, BVF2 and Trading Fund OS and held in the Partners Managed Account, representing percentage ownership of approximately 22.3% of the Shares outstanding. BVF Inc., as the general partner of Partners, may be deemed to beneficially own the 16,001,284 Shares beneficially owned by Partners, representing percentage ownership of approximately 22.3% of the Shares outstanding. Mr. Lampert, as a director and officer of BVF Inc., may be deemed to beneficially own the 16,001,284 Shares beneficially owned by BVF Inc., representing percentage ownership of approximately 22.3% of the Shares outstanding. As of the date hereof, Mr. Loy beneficially owned 18,985 Shares, which consist of Shares issuable upon the exercise of certain options that are exercisable within sixty days hereof, representing percentage ownership of less than 1%. The foregoing should not be construed in and of itself as an admission by any Reporting Person as to beneficial ownership of any Shares owned by another Reporting Person. BVF GP disclaims beneficial ownership of the Shares beneficially owned by BVF. BVF2 GP disclaims beneficial ownership of the Shares beneficially owned by BVF2. Partners OS disclaims beneficial ownership of the Shares beneficially owned by Trading Fund OS. BVF GPH disclaims beneficial ownership of the Shares beneficially owned by BVF and BVF2. Each of Partners, BVF Inc. and Mr. Lampert disclaims beneficial ownership of the Shares beneficially owned by BVF, BVF2 and Trading Fund OS and held in the Partners Managed Account. Mr. Loy disclaims beneficial ownership of the Shares reported herein that he does not directly own.
(b)	Item 5(b) is hereby amended and restated to read as follows: Each of BVF, BVF2 and Trading Fund OS shares with Partners voting and dispositive power over the Shares each such entity beneficially owns. BVF shares with BVF GP voting and dispositive power over the Shares beneficially owned by BVF. BVF2 shares with BVF2 GP voting and dispositive power over the Shares beneficially owned by BVF2. Each of BVF GP and BVF2 GP shares with BVF GPH voting and dispositive power over the Shares each such entity beneficially owns. Trading Fund OS shares with Partners OS voting and dispositive power over the Shares beneficially owned by Trading Fund OS. Partners, BVF Inc. and Mr. Lampert share voting and dispositive power over the Shares they may be deemed to beneficially own with BVF, BVF GP, BVF2, BVF2 GP, Trading Fund OS, Partners OS and BVF GPH and held in the Partners Managed Account.
(c)	Item 5(c) is hereby amended and restated to read as follows: On March 31, 2026, (i) BVF sold 1,932,354 Shares at a price of $16.79 per Share, (ii) BVF2 sold 1,569,116 Shares at a price of $16.79 per Share, and (iii) Trading Fund OS sold 248,530 Shares at a price of $16.79 per Share. Except as set forth herein, none of the Reporting Persons has entered into any transactions in the securities of the Issuer during the past 60 days.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

BIOTECHNOLOGY VALUE FUND L P

Signature:	/s/ Mark N. Lampert
Name/Title:	Mark N. Lampert, Authorized Signatory
Date:	04/02/2026

BVF I GP LLC

Signature:	/s/ Mark N. Lampert
Name/Title:	Mark N. Lampert, Authorized Signatory
Date:	04/02/2026

BIOTECHNOLOGY VALUE FUND II LP

Signature:	/s/ Mark N. Lampert
Name/Title:	Mark N. Lampert, Authorized Signatory
Date:	04/02/2026

BVF II GP LLC

Signature:	/s/ Mark N. Lampert
Name/Title:	Mark N. Lampert, Authorized Signatory
Date:	04/02/2026

Biotechnology Value Trading Fund OS LP

Signature:	/s/ Mark N. Lampert
Name/Title:	Mark N. Lampert, Authorized Signatory
Date:	04/02/2026

BVF Partners OS Ltd.

Signature:	/s/ Mark N. Lampert
Name/Title:	Mark N. Lampert, Authorized Signatory
Date:	04/02/2026

BVF GP HOLDINGS LLC

Signature:	/s/ Mark N. Lampert
Name/Title:	Mark N. Lampert, Authorized Signatory
Date:	04/02/2026

BVF PARTNERS L P/IL

Signature:	/s/ Mark N. Lampert
Name/Title:	Mark N. Lampert, Authorized Signatory
Date:	04/02/2026

BVF INC/IL

Signature:	/s/ Mark N. Lampert
Name/Title:	Mark N. Lampert, Authorized Signatory
Date:	04/02/2026

LAMPERT MARK N

Signature:	/s/ Mark N. Lampert
Name/Title:	Mark N. Lampert
Date:	04/02/2026

Loy Spike

Signature:	/s/ Spike Loy
Name/Title:	Spike Loy
Date:	04/02/2026

FAQ

What stake does BVF hold in MoonLake (MLTX) after this Schedule 13D/A?

BVF and its affiliated entities report beneficial ownership of 16,001,284 MoonLake shares, representing about 22.3% of the 71,727,875 shares outstanding as of February 1, 2026. This consolidates positions held across multiple BVF funds and a managed account.

Which BVF entities are the main MoonLake (MLTX) shareholders in this filing?

Biotechnology Value Fund, L.P. holds 8,302,735 shares (about 11.6%), Biotechnology Value Fund II holds 6,599,722 shares (about 9.2%), and Biotechnology Value Trading Fund OS holds 1,039,238 shares (about 1.4%). These are managed together with smaller positions in a Partners Managed Account.

What MoonLake (MLTX) share sales did BVF report on March 31, 2026?

On March 31, 2026, BVF sold 1,932,354 MoonLake shares at $16.79 each, BVF II sold 1,569,116 shares at $16.79, and Biotechnology Value Trading Fund OS sold 248,530 shares at $16.79. These transactions reduced but did not eliminate their large combined stake.

How is BVF Partners L.P. involved in the MoonLake (MLTX) holdings?

BVF Partners L.P., as investment manager for BVF, BVF II, Biotechnology Value Trading Fund OS and a managed account, may be deemed to beneficially own 16,001,284 MoonLake shares, or about 22.3% of the class. It shares voting and dispositive power with affiliated general partner entities.

What is the outstanding share count used in this MoonLake (MLTX) 13D/A?

The filing bases all percentage ownership figures on 71,727,875 MoonLake Class A ordinary shares outstanding as of February 1, 2026, as reported in the company’s Form 10-K filed on February 25, 2026. All BVF complex ownership percentages are calculated against this share count.

What is Spike Loy’s reported MoonLake (MLTX) ownership in this amendment?

Spike Loy is reported as beneficially owning 18,985 MoonLake shares, representing about 0.03% of the class. These shares consist of options that are exercisable within sixty days, awarded in connection with his service as a director of MoonLake.