November 2, 2018

Jack A. Khattar
President and Chief Executive Officer
Supernus Pharmaceuticals, Inc.
1550 East Gude Drive
Rockville, MD 20850

       Re: Supernus Pharmaceuticals, Inc.
           Form 10-K for the Fiscal Year Ended December 31, 2017
           Filed March 1, 2018
           File No. 001-35518

Dear Mr. Khattar:

       We have reviewed your October 5, 2018 response to our comment letter and
have the
following comments. In some of our comments, we may ask you to provide us with
information
so we may better understand your disclosure.

       Please respond to these comments within 10 business days by providing
the requested
information or advise us as soon as possible when you will respond. If you do
not believe our
comments apply to your facts and circumstances, please tell us why in your
response.

      After reviewing your response to these comments, we may have additional
comments. Unless we note otherwise, our references to prior comments are to
comments in our
September 21, 2018 letter.

Form 10-K for the Fiscal Year Ended December 31, 2017

Management's Discussion and Analysis of Financial Condition and Results of
Operations
Critical Accounting Policies and Use of Estimates
Revenue Recognition, page 64

1.    It appears from your response to prior comment 1 that your gross-to-net
adjustments
      recorded in 2016 related to sales of prior years was significant to your
operating earnings
      and earnings before income taxes in 2016. To the extent that re-estimates
of prior year
      gross-to-net variable consideration is significant in future periods,
please represent to us
      that you will disclose herein the impact on your product sales and
operating results and
      include in your financial statements the disclosure required by ASC
606-10-50-12A.
 Jack A. Khattar
Supernus Pharmaceuticals, Inc.
November 2, 2018
Page 2
2.       It appears from your response to prior comment 1 that your
gross-to-net adjustment for
         sales returns of Oxtellar XR recorded in 2016 related to prior period
sales was significant
         to your net product sales for Oxtellar XR in 2016 and to your
estimated reserve balance at
         December 31, 2015. Given the magnitude of this adjustment recorded in
2016, please tell
         us how you were able to make reasonable estimates of product returns
in order to
         recognize product sales of Oxtellar XR revenue upon product shipment
under ASC 605-
         15-25-1f applicable at the time.
       You may contact Bonnie Baynes at (202) 551-4924 or Mark Brunhofer at
(202) 551-3638
with any questions.



FirstName LastNameJack A. Khattar                             Sincerely,
Comapany NameSupernus Pharmaceuticals, Inc.
                                                              Division of
Corporation Finance
November 2, 2018 Page 2                                       Office of
Healthcare & Insurance
FirstName LastName