Exhibit 31.3
CERTIFICATION PURSUANT TO
EXCHANGE ACT RULES 13a-14(a) AND 15d-14(a), AS ADOPTED PURSUANT TO
SECTION 302 OF THE SARBANES-OXLEY ACT OF 2002
I, Johnson Y.N. Lau, certify that:
| 1. | I have reviewed this Amendment No. 1 to the Annual Report on Form 10-K of Athenex, Inc.; and |
| 2. | Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report. |
Date: April 28, 2023
| /s/ Johnson Y.N. Lau |
| Name: Johnson Y.N. Lau |
| Title: Chief Executive Officer and Board Chairman |
| (Principal Executive Officer) |