Expiry of the patent may be extended as we saw in the PD1-Vaxx...

Expiry of the patent may be extended as we saw in the PD1-Vaxx patent announcement 3 weeks ago:

"Sydney, Australia, 29 June 2023: Imugene Limited (ASX: IMU), a clinical stage
immuno-oncology company, is pleased to announce the grant of a new patent
(number 11,684,929) by the United States Patent Office. The granted claims protect
Imugene’s immunotherapeutic PD1-Vaxx, a first-in-class programmed death-1 (PD1)
vaccine, currently in clinical development for non-small cell lung cancer (NSCLC).
The patent titled “HUMAN PD1 PEPTIDE VACCINES AND USES THEREOF” will expire on 11
February 2040 (including 685 days of patent term adjustment added to the original
expiry date of 28 March 2038) and protects the composition of matter and method of
treatment in cancer of Imugene’s PD1-Vaxx for the generation of a therapeutic
antibody response against the PD1 checkpoint target."

Holding some patents myself I can assure you it is a long and complicated process taking years, although mine are just of technical nature.
In Biotech, as research moves on quickly, term adjustments might be more common and even if a patent expires you could file new applications while combining it with other treatments. At least this is the way big pharma tries to protect their IP for as long as they could.