The making of CVM's mixture of immuno-reactive proteins is complex. Anybody trying to duplicate it would first have to build out a facility like CVM has and get the right quality controls in place.
Manufacture of Multikine is also a Trade Secret in a lot of ways. Somebody who wanted to manufacture a generic or alternative version of Multikine would likely have to acquire CVM's Trade Secrets (illicitly) or buy the rights to use those Trade Secrets from CVM. In some ways, Trade Secrets are better than Patents - as long as you can keep them a secret they don't really ever expire. :D
A competitor could try and reverse engineer a Multikine equivalent, but my guess is that's not overly simple, and it would probably just be easier to buy out CVM in some way IF they want the drug.
And don’t forget that Multikine received orphan drug designation from the FDA and 7 years of market exclusivity. Even if the parents expire, FDA won’t approve a competing product.