Company: SUPN
Filing Date: 2025-02-24
Form Type: S-8 POS
Source: 0001104659-25-016557
Chunk: 1

Company: SUPERNUS PHARMACEUTICALS, INC.
Filing Date: 2025-02-24
Form: S-8 POS
Chunk 1
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 growth Registrant, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act.¨

<div align='center'>EXPLANATORY NOTE</div>

Supernus Pharmaceuticals, Inc., a Delaware
corporation (the “Registrant”) previously filed its Registration Statement on Form S-8 (Registration No. 333-181479) with the United States Securities and Exchange Commission (the “SEC”) on May 17, 2012 (the “Registration Statement”)
with respect to 3,301,490 shares of the Registrant’s Common Stock, par value $0.001 per share (the “Shares”), issuable
under the Supernus Pharmaceuticals, Inc. 2005 Stock Plan, the Supernus Pharmaceuticals, Inc. 2012 Equity Incentive Plan, and
the Supernus Pharmaceuticals, Inc. 2012 Employee Stock Purchase Plan (collectively, the “Plans”)

The Registrant is filing this Post-Effective Amendment
No. 1 to its Registration Statement on Form S-8 (Registration No. 333-181479) (this “Post-Effective Amendment”)
to terminate all offerings under the Registration Statement because all of the Shares have been sold.

<div align='center'>SIGNATURES</div>

Pursuant to the requirements of the Securities
Act of 1933, the Registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-8
and has duly caused this post-effective amendment to be signed on its behalf by the undersigned, thereunto duly authorized, in the City
of Rockville, State of Maryland, on February 24, 2025.

| SUPERNUS PHARMACEUTICALS, INC.               |                     |
| By:                                          | /s/ Jack A. Khattar |
| Name: Jack A. Khattar                        |                     |
| Title: President and Chief Executive Officer |                     |

Pursuant to the requirements of the Securities Act of 1933, this registration
statement has been signed below by the following persons in the capacities and on the date indicated.

| Signature                        
 /s/ Jack A. Khattar              |     | Title                                                         
 President and Chief Executive Officer and Director            |     | Date              
 February 24, 2025 |
|:--------------------------------