SEC Form 4

FORM 4		UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940	OMB APPROVAL OMB Number: 3235-0287 Estimated average burden hours per response: 0.5
	Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person* CAVAZZA PAOLO (Last) (First) (Middle) VIA TESSERETE 10 (Street) LUGANO V8 0000 (City) (State) (Zip)	2. Issuer Name and Ticker or Trading Symbol REGENERX BIOPHARMACEUTICALS INC [ RGN ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director X 10% Owner Officer (give title below) Other (specify below)
	3. Date of Earliest Transaction (Month/Day/Year) 05/21/2010
	4. If Amendment, Date of Original Filed (Month/Day/Year)	6. Individual or Joint/Group Filing (Check Applicable Line) X Form filed by One Reporting Person Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	05/21/2010		P(1)		240,000	A	(1)	240,000	I(2)	Indirect(2)
Common Stock								8,175,110(3)(4)(5)	I(6)	Indirect(6)
Common Stock								12,011,185(7)	I(8)	Indirect(8)
Common Stock								984,615	I(9)	Indirect(9)

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Common Stock Warrants (right to buy)	$0.56	05/21/2010		P(1)		96,000		05/21/2010	05/21/2015	Common Stock	96,000	(1)	96,000	I(2)	Indirect(2)

Explanation of Responses:

1. These securities were purchased as part of Units purchased by the reporting person directly from the underwriters in the Issuer's public offering that closed on May 21, 2010 for $0.41 per Unit. Each Unit consisted of one share of Common Stock and 0.4 Warrants to purchase Common Stock. The Units separated immediately.

2. Securities directly owned by Sinaf SA ("Sinaf") which is a direct wholly-owned subsidiary of Aptafin S.p.A. ("Aptafin"). Aptafin is owned by Paolo Cavazza and members of his family.

3. 1,219,512 of these shares were acquired on October 8, 2009 pursuant to a purchase agreement dated as of September 30, 2009 with the Issuer that provides that the Issuer, rather than Chaumiere Consultadoria e Servicos SDC Unipessoal L.d.a. ("Chaumiere"), has all voting rights in respect of the shares through September 30, 2012, and that Chaumiere may not transfer the shares through September 30, 2012 except for transfers to Affiliates (as defined therein). 1,052,631 of these shares were acquired on April 13, 2009 pursuant to a purchase agreement with the Issuer that provides that the Issuer, rather than Chaumiere, has all voting rights in respect of the shares through April 30, 2012, and that Chaumiere may not transfer the shares through April 30, 2012 except for transfers to Affiliates (as defined therein). 1,034,482 of these shares were acquired on December 10, 2008 pursuant to a purchase agreement with the Issuer that provides that the Issuer, rather than Chaumiere, has all voting

4. rights in respect of such shares through December 31, 2011, and that Chaumiere may not transfer such shares through December 31, 2011 except for transfers to Affiliates (as defined therein). 2,500,000 of these shares were acquired on February 29, 2008 pursuant to a purchase agreement with the Issuer that provides that the Issuer has the right to repurchase the shares at any time until December 31, 2010, for $2.50 per share. Furthermore, the purchase agreement provides that the Issuer, rather than Chaumiere, has all voting rights in respect of the shares through December 31, 2010, and that Chaumiere may not transfer such shares through December 31, 2010 except for transfers to Affiliates (as defined therein). 923,077 of these shares were acquired on June 22, 2005 pursuant to a purchase agreement with the Issuer that provides Chaumiere may not dispose of the shares for a five-year period (the "Holding Period"), that the Issuer, rather than Chaumiere,

5. has all voting rights in respect of the shares during the Holding Period, and that the Issuer shall have the right to repurchase the shares within 30 days of the expiration of the Holding Period at a price of $5.00 per share, provided that the Issuer may only repurchase an amount of shares that would leave Chaumiere, when combined with all of its affiliates, with no less than 30.1% of the Issuer's shares of Common Stock.

6. Securities directly owned by Chaumiere, which is a direct wholly-owned subsidiary of Sinaf and an indirect wholly-owned subsidiary of Aptafin.

7. 307,692 of these shares were acquired on June 22, 2005 pursuant to a purchase agreement with the Issuer that provides that Defiante (as defined below) may not dispose of the shares during the Holding Period, that the Issuer, rather than Defiante, has all voting rights in respect of the shares during the Holding Period, and that the Issuer shall have the right to repurchase the shares within 30 days of the expiration of the Holding Period at a price of $5.00 per share, provided that the Issuer may only repurchase an amount of shares that would leave Defiante, when combined with all of its affiliates, with no less than 30.1% of the Issuer's shares of Common Stock.

8. Securities directly owned by Defiante Farmaceutica S.A. ("Defiante"). Defiante is 58% directly owned by Sigma Tau Finanziaria S.p.A. ("Sigma Tau") and 42% directly owned by Sigma Tau's wholly-owned subsidiary, Sigma Tau International S.A. Paolo Cavazza directly and indirectly owns 38% of Sigma Tau.

9. Securities directly owned by Sigma Tau.

Remarks:

	/s/Fabio Poma, Attorney-in-fact	05/25/2010
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
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