Aisling Capital Iii SC 13D Loxo Oncology, Inc.

EXHIBIT 4

JOINT FILING AGREEMENT

Each of the undersigned hereby acknowledges and agrees, in compliance with the provisions of Rule 13d-1(k)(1) promulgated under the Securities Exchange Act of 1934, as amended, that the Schedule 13D to which this Agreement is attached as an Exhibit (the “Schedule 13D”), and any amendments thereto, will be filed with the Securities and Exchange Commission jointly on behalf of the undersigned. This Agreement may be executed in one or more counterparts.

Date: May 27, 2016

	AISLING CAPITAL III, LP
By:	Aisling Capital Partners III, LP General Partner
By:	Aisling Capital Partners III LLC General Partner
	By:	/s/ Dennis Purcell
		Name: Dennis Purcell
		Title: Managing Member

	AISLING CAPITAL PARTNERS III, LP
By:	Aisling Capital Partners III LLC General Partner
	By:	/s/ Dennis Purcell
		Name: Dennis Purcell
		Title: Managing Member

	AISLING CAPITAL PARTNERS III LLC
By:	/s/ Dennis Purcell
	Name: Dennis Purcell Title: Managing Member
	/s/ Steven Elms
	Steven Elms
	/s/ Dennis Purcell
	Dennis Purcell
	/s/ Andrew Schiff
	Andrew Schiff