13D Filing: James E. Flynn and AveXis Inc (AVXS)

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

[Rule 13d-101]

INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO §
24.13d-1(a) AND AMENDMENTS THERETO FILED PURSUANT TO § 240.13D-2(a)

(Amendment No. 4)*

AveXis,
Inc.

(Name
of Issuer)

Common
Stock, par value $0.0001 per share

(Title
of Class of Securities)

05366U100

(CUSIP
Number)

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

September
6, 2017

(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 ☐.

Note: Schedules
filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See § 240.13d-7
for other parties to whom copies are to be sent.

(Continued on following
pages)

(Page 1 of 15 Pages)

* The remainder of this cover page shall be filled out for a
reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment
containing information which would alter disclosures provided in a prior cover page.

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).

SCHEDULE 13D

(1) Comprised of 230,585 shares held by Deerfield Special Situations
Fund, L.P., 160,143 shares held by Deerfield Partners, L.P. and 111,286 shares held by Deerfield International Master Fund, L.P.

 SCHEDULE 13D

 SCHEDULE 13D

 SCHEDULE 13D

SCHEDULE 13D

SCHEDULE 13D

(2) Comprised of 230,585 shares held by Deerfield Special Situations
Fund, L.P., 160,143 shares held by Deerfield Partners, L.P., 1,343,202 shares held by Deerfield Private Design Fund III, L.P.,
111,286 shares held by Deerfield International Master Fund, L.P. and 12,646 shares held directly by Deerfield Management Company,
L.P.

SCHEDULE 13D

(3) Comprised of 1,343,202 shares held by Deerfield Private Design Fund III, L.P.

SCHEDULE 13D

(4) Comprised of 230,585 shares held by Deerfield Special Situations
Fund, L.P., 160,143 shares held by Deerfield Partners, L.P., 1,343,202 shares held by Deerfield Private Design Fund III, L.P.,
111,286 shares held by Deerfield International Master Fund, L.P. and 12,646 shares held by Deerfield Management Company, L.P.

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 Special Situations Fund, L.P. (“Deerfield Special Situations
Fund”), (iii) Deerfield Management Company, L.P. (“Deerfield Management”), (iv) Deerfield Private
Design Fund III, L.P. (“Deerfield Private Design Fund III”), (v) Deerfield Partners, L.P. (“Deerfield
Partners”), (vi) Deerfield International Master Fund, L.P. (“Deerfield International Master Fund”),
(vii) Deerfield Mgmt III, L.P. (“Deerfield Mgmt III”) and (viii) James E. Flynn, a natural person (“Flynn”
and collectively with Deerfield Mgmt, Deerfield Special Situations Fund, Deerfield Management, Deerfield Private Design Fund III,
Deerfield Partners, Deerfield International Master Fund and Deerfield Mgmt III, the “Reporting Persons”), with
respect to the securities of AveXis, Inc. (the “Company”), on February 19, 2016, as amended by Amendment Nos.
1, 2 and 3 to the Schedule 13D filed on February 2, 2017, May 31, 2017 and August 22, 2017. Deerfield Special Situations Fund,
Deerfield Private Design Fund III, Deerfield Partners and Deerfield International Master Fund are collectively referred to herein
as the “Funds.”

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

Items 5(a), (b) and (c) of the Schedule 13D are hereby amended
and restated in their entirety as follows:

(a)

(1)       Deerfield
Mgmt

Percentage of shares: 1.57%*

(2)       Deerfield
Management

Percentage of shares: 5.82%*

(3)       Deerfield
Special Situations Fund

Number of shares: 230,585

Percentage of shares: 0.72%*

(4)       Deerfield
Private Design Fund III

Number of shares: 1,343,202

Percentage of shares: 4.21%*

(5)       Deerfield Partners

Number of Shares: 160,143

Percentage of Shares: 0.50%*

(6)       Deerfield
International Master Fund

Number of Shares: 111,286

Percentage of Shares: 0.35%*

(7)       Deerfield
Mgmt III

Percentage of shares: 4.21%*

(8)       Flynn

Percentage of shares: 5.82%*

*Percentage beneficial ownership reported herein reflects 31,938,092
shares of Common Stock outstanding, based on 31,925,446 shares of Common Stock outstanding as of August 10, 2017, as reported in
the Company’s Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2017, plus 12,646 shares of Common Stock
held by Deerfield Management, which were issued upon exercise of options held by Jonathan Leff.

(b)

(1)       Deerfield
Mgmt

Sole power to vote or direct the vote:
0

Shared power to vote or direct the vote:
502,014

Sole power to dispose or to direct the
disposition: 0

Shared power to dispose or direct the disposition:
502,014

(2)       Deerfield
Management

Sole power to vote or direct the vote:
0

Shared power to vote or direct the vote:
1,857,862

Sole power to dispose or to direct the
disposition: 0

Shared power to dispose or direct the disposition:
1,857,862

(3)       Deerfield
Special Situations Fund

Sole power to vote or direct the vote:
0

Shared power to vote or direct the vote:
230,585

Sole power to dispose or to direct the
disposition: 0

Shared power to dispose or direct the disposition:
230,585

(4)       Deerfield
Private Design Fund III

Sole power to vote or direct the vote:
0

Shared power to vote or direct the vote:
1,343,202

Sole power to dispose or to direct the
disposition: 0

Shared power to dispose or direct the disposition:
1,343,202

(5)       Deerfield
Partners

Sole power to vote or direct the vote:
0

Shared power to vote or direct the vote:
160,143

Sole power to dispose or to direct the
disposition: 0

Shared power to dispose or direct the disposition:
160,143

(6)       Deerfield
International Master Fund

Sole power to vote or direct the vote:
0

Shared power to vote or direct the vote:
111,286

Sole power to dispose or to direct the
disposition: 0

Shared power to dispose or direct the disposition:
111,286

(7)       Deerfield
Mgmt III

Sole power to vote or direct the vote:
0

Shared power to vote or direct the vote:
1,343,202

Sole power to dispose or to direct the
disposition: 0

Shared power to dispose or direct the disposition:
1,343,202

(8)       Flynn

Sole power to vote or direct the vote:
0

Shared power to vote or direct the vote:
1,857,862

Sole power to dispose or to direct the
disposition: 0

Shared power to dispose or direct the disposition:
1,857,862

Flynn is the sole member of the general
partner of each of Deerfield Mgmt, Deerfield Mgmt III and Deerfield Management. Deerfield Mgmt is the general partner, and Deerfield
Management is the investment advisor, of Deerfield Special Situations Fund, Deerfield Partners and Deerfield International Master
Fund. Deerfield Mgmt III is the general partner, and Deerfield Management is the investment advisor, of Deerfield Private Design
Fund III.

(c) Transactions in the Common Stock effected
by the Reporting Persons since the filing of Amendment No. 3 to the Schedule 13D are set forth on Schedule A to this Amendment.
Except for the Leff Option Exercise (as defined in Schedule A to this Amendment) and the Rebalancing Trade (as defined in Schedule
A to this Amendment), all of the transactions reflected in Schedule A to this Amendment were effected in open market transactions
on the Nasdaq Global Select Market in the ordinary course of the applicable Reporting Person’s business.

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: September 8, 2017

Schedule A

*Except as otherwise indicated in footnote (1), each price per
share reported in the “Price per Share” column of this Schedule A is a weighted average price. The Reporting Persons
undertake to provide to the staff of the Securities and Exchange Commission, upon request, full information regarding the number
of shares sold at each separate price within the ranges set forth in the “Price Range” column of this Schedule A.

**Except as otherwise indicated in footnote (1), the shares
were sold in multiple transactions at prices within the price range indicated.

(1) The shares were sold in multiple transactions at a single
price of $94.30 per share.

In addition to the transactions set forth
in the table above: