As filed with the Securities and Exchange Commission on December 19, 2025 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 AMENDMENT NO. 4 TO FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 iSpecimen Inc. (Exact name of registrant as specified in its charter) Delaware 8731 27-0480143 (State or jurisdiction of incorporation or organization) (Primary Standard Industrial Classification Code Number) (IRS Employer Identification No.) 8 Cabot Road, Suite 1800 Woburn, MA 081 ...

UNDER THE SECURITIES ACT OF 1933 As filed with the Securities and Exchange Commission on August 25, 2025 Registration No. 333-289725 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 AMENDMENT NO. 1 TO FORM S-1 REGISTRATION STATEMENT iSpecimen, Inc. (Exact name of registrant as specified in its charter) (State or jurisdiction of incorporation or organization) (Primary Standard Industrial Classification Code Number) Delaware 8731 27-0480143 (IRS Employer Identification No.) 8 Cabot Road ...