One of The Largest Hedge Funds In The World Is Betting On Loxo Oncology Inc. (LOXO)

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Page 11 of 11 – SEC Filing

EXHIBIT 1

JOINT FILING AGREEMENT
PURSUANT TO RULE 13d-1(k)

The undersigned acknowledge and agree that the foregoing statement
on Schedule 13G is filed on behalf of each of the undersigned and that all subsequent amendments to this statement on Schedule
13G shall be filed on behalf of each of the undersigned without the necessity of filing additional joint filing agreements. The
undersigned acknowledge that each shall be responsible for the timely filing of such amendments, and for the completeness and accuracy
of the information concerning him or it contained herein and therein, but shall not be responsible for the completeness and accuracy
of the information concerning the others, except to the extent that he or it knows or has reason to believe that such information
is inaccurate.

DATE: January 6, 2017

ADAGE CAPITAL PARTNERS, L.P.
By:  Adage Capital Partners GP, L.L.C.,
its general partner
By:  Adage Capital Advisors, L.L.C.,
its managing member
/s/ Robert Atchinson
Name:  Robert Atchinson
Title: Managing Member
ADAGE CAPITAL PARTNERS GP, L.L.C.
By:  Adage Capital Advisors, L.L.C.,
its managing member
/s/ Robert Atchinson
Name:  Robert Atchinson
Title: Managing Member
ADAGE CAPITAL ADVISORS, L.L.C.
/s/ Robert Atchinson
Name:  Robert Atchinson
Title: Managing Member
/s/ Robert Atchinson
ROBERT ATCHINSON, individually
/s/ Phillip Gross
PHILLIP GROSS, individually

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