Company: SUPN
Filing Date: 2025-02-24
Form Type: S-8 POS
Source: 0001104659-25-016557
Chunk: 0

Company: SUPERNUS PHARMACEUTICALS, INC.
Filing Date: 2025-02-24
Form: S-8 POS
Chunk 0
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<div align='center'>As filed with the Securities and Exchange Commission
on February 24, 2025</div>

Registration No. 333-181479

<div align='center'>UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

POST-EFFECTIVE AMENDMENT NO. 1 TO FORM S-8

REGISTRATION STATEMENT

UNDER THE SECURITIES ACT OF 1933

SUPERNUS PHARMACEUTICALS, INC.

(Exact name of registrant as specified in its charter)</div>

| Delaware                                                       
 (State or other jurisdiction of incorporation or organization) | 20-2590184                           
 (I.R.S. Employer Identification No.) |
| 9715 Key West Avenue, Rockville, MD                            
 (Address of principal executive offices)                       | 20850                                
 (Zip Code)                           |

<div align='center'>Supernus Pharmaceuticals, Inc. 2005 Stock Plan

Supernus Pharmaceuticals, Inc. 2012 Equity Incentive Plan

Supernus Pharmaceuticals, Inc. 2012 Stock Purchase Plan

(Full titles of the plans)

Jack A. Khattar

President and Chief Executive Officer

Supernus Pharmaceuticals, Inc.

9715 Key West Avenue

Rockville, Maryland 20850

(301) 838-2500

(Name, address, including zip code, and telephone
number, including area code, of agent for service)

Copy of all communications to:

Mark I. Gruhin, Esquire

George A. Naya, Esquire

Saul Ewing LLP

1919 Pennsylvania Avenue, N.W.
Suite 550
Washington, DC 20006-3434
(202) 333-8800</div>

Indicate by check mark whether the registrant
is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting Registrant or an emerging growth Registrant.
See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting Registrant,”
and “emerging growth Registrant” in Rule 12b-2 of the Exchange Act.

| Large accelerated filer    | x | Accelerated filer            | ¨ |
| Non-accelerated filer      | ¨ | Smaller reporting Registrant | ¨ |
| Emerging growth Registrant | ¨ |                              |   |

If an emerging