SCHEDULE 13D 

(1) Consists of shares of Class A Common Stock held by Deerfield Partners, L.P. and Deerfield International Master Fund, L.P., of each of which Deerfield Mgmt, L.P. is the general partner. The percentage of outstanding Class A Common Stock beneficially owned has been determined based on 16,395,599 shares of Class A Common Stock outstanding as of November 7, 2016, as set forth in the Company’s Quarterly Report on Form 10-Q for the quarterly period ended September 30, 2016.

 SCHEDULE 13D

(2) Consists of shares of Class A Common Stock held by Deerfield Partners, L.P. and Deerfield International Master Fund, L.P., of each of which Deerfield Management Company, L.P. is the investment adviser. The percentage of outstanding Class A Common Stock beneficially owned has been determined based on 16,395,599 shares of Class A Common Stock outstanding as of November 7, 2016, as set forth in the Company’s Quarterly Report on Form 10-Q for the quarterly period ended September 30, 2016.

SCHEDULE 13D

(3) The percentage of outstanding Class A Common Stock beneficially owned has been determined based on 16,395,599 shares of Class A Common Stock outstanding as of November 7, 2016, as set forth in the Company’s Quarterly Report on Form 10-Q for the quarterly period ended September 30, 2016.

 SCHEDULE 13D

(4) The percentage of outstanding Class A Common Stock beneficially owned has been determined based on 16,395,599 shares of Class A Common Stock outstanding as of November 7, 2016, as set forth in the Company’s Quarterly Report on Form 10-Q for the quarterly period ended September 30, 2016.

SCHEDULE 13D

(5) Consists of shares of Class A Common Stock held by Deerfield Partners, L.P. and Deerfield International Master Fund, L.P. James E. Flynn is the managing member of the general partner of each of Deerfield Mgmt, L.P. and Deerfield Management Company, L.P., the general partner and the investment adviser, respectively, of Deerfield Partners, L.P. and Deerfield International Master Fund, L.P. The percentage of outstanding Class A Common Stock beneficially owned has been determined based on 16,395,599 shares of Class A Common Stock outstanding as of November 7, 2016, as set forth in the Company’s Quarterly Report on Form 10-Q for the quarterly period ended September 30, 2016.

This Amendment No. 4 (this “ Amendment ”) to Schedule 13D amends the Schedule 13D (as previously amended, the “ Schedule 13D ”) filed by (i) Deerfield Mgmt, L.P. (“ Deerfield Mgmt ”), (ii) Deerfield Management Company, L.P. (“ Deerfield Management ”), (iii) Deerfield Partners, L.P. (“ Deerfield Partners ”), (iv) Deerfield International Master Fund, L.P. (“ DIMF ” and, together with Deerfield Partners, collectively referred to herein as the “ Funds ”) and (v) James E. Flynn, a natural person (“ Flynn ” and, collectively with Deerfield Mgmt, Deerfield Management, Deerfield Partners, and DIMF, the “ Reporting Persons ”), with respect to the securities of Adeptus Health Inc. (the “ Company ”), on September 19, 2016, as amended by Amendment Nos. 1, 2 and 3 thereto, filed by the Reporting Persons on February 6, 2017, April 4, 2017 and April 20, 2017, respectively.

Capitalized terms used herein but not otherwise defined herein shall have the meanings ascribed to them in the Schedule 13D.

Item 4.     Purpose of Transaction.

Item 4 of the Schedule 13D is hereby supplemented and amended as follows:

The information set forth under Item 6 of this Amendment is incorporated herein by reference.

Item 5.     Interests in Securities of the Issuer

Item 5 of the Schedule 13D is hereby amended and restated in its entirety to read as follows:

(a) Throughout this report, the percentage of outstanding Common Stock beneficially owned by the Reporting Persons has been determined based on 16,395,599 shares of Common Stock outstanding as of November 7, 2016, as set forth in the Company’s Quarterly Report on Form 10-Q for the quarterly period ended September 30, 2016.

(1) Deerfield Management

Number of shares: 798,297

Percentage of shares: 4.87%

(2) Deerfield Mgmt

Number of shares: 798,297

Percentage of shares: 4.87%

(3) Deerfield Partners

Number of shares: 351,252

Percentage of shares: 2.14%

(4) DIMF

Number of shares: 447,045

Percentage of shares: 2.73%

(5) Flynn

Number of shares: 798,297

Percentage of shares: 4.87%

(b)

(1) Deerfield Management

Sole power to vote or direct the vote: 0

Shared power to vote or direct the vote: 798,297

Sole power to dispose or to direct the disposition: 0

Shared power to dispose or direct the disposition: 798,297

(2) Deerfield Mgmt

Sole power to vote or direct the vote: 0

Shared power to vote or direct the vote: 798,297

Sole power to dispose or to direct the disposition: 0

Shared power to dispose or direct the disposition: 798,297

(3) Deerfield Partners

Sole power to vote or direct the vote: 0

Shared power to vote or direct the vote: 351,252

Sole power to dispose or to direct the disposition: 0

Shared power to dispose or direct the disposition: 351,252

(4) DIMF

Sole power to vote or direct the vote: 0

Shared power to vote or direct the vote: 447,045

Sole power to dispose or to direct the disposition: 0

Shared power to dispose or direct the disposition: 447,045

(5) Flynn

Sole power to vote or direct the vote: 0

Shared power to vote or direct the vote: 798,297

Sole power to dispose or to direct the disposition: 0

Shared power to dispose or direct the disposition: 798,297

Flynn is the managing member of the general partner of each of Deerfield Mgmt and Deerfield Management.  Deerfield Mgmt is the general partner, and Deerfield Management is the investment adviser, of each Fund. Each of the Funds directly owns the shares shown as beneficially owned by such Fund.

(c) Except as disclosed in Item 4, no Reporting Person has effected any transactions in the Common Stock during the past 60 days.

(d) Not Applicable.

(e) As of May 12, 2017, the Reporting Persons ceased to beneficially own more than five percent of the Common Stock.

Item 6.     Contracts, Arrangements, Understandings or Relationships With Respect to Securities of the Issuer.

Item 6 of the Schedule 13D is hereby amended and supplemented by adding the following:

On May 9, 2017, each of Deerfield Partners and DIMF entered into a Stock Purchase Agreement (the “SPA”) pursuant to which it agreed to sell 353,128 shares and 449,434 shares of Common Stock (collectively, the “Subject Shares”), respectively, for an aggregate purchase price of $500, in order to liquidate a significant portion of its equity investment in the Company for a sum certain. Pursuant to the SPA, the purchaser agreed to certain limitations on the resale of the Subject Shares. The sale of the Subject Shares was completed on May 12, 2017.

The foregoing description of the SPA is a summary only and is qualified in its entirety by reference to the full text of the SPA, a copy of which is filed as Exhibit 99.2 hereto.

Item 7.     Material to be Filed as Exhibits.

Item 7 of the Schedule 13D is hereby amended by adding the following as Exhibits 99.2:

Exhibit 99.2     Form of Stock Purchase Agreement*

SIGNATURE

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

Dated: May 12, 2017

Exhibit Index

Exhibit 99.2     Form of Stock Purchase Agreement