Ligand Pharmaceuticals Inc. has spent $4 million to acquire a portfolio of more than 15 biologic development programs from Swiss biotech firm Selexis SA, which could provide future milestone and royalty payments.

The programs are in various stages of development, from pre-clinical trials through Phase 3 testing, and each is already fully funded by a development partner.

Each program involves Selexis’ proprietary technology for manufacturing cell lines to be used in biologic therapeutics.

Ligand CEO John Higgins said such acquisitions “are a great fit with our royalty-based business model,” in a news release.

La Jolla-based Ligand (Nasdaq: LGND) made a similar acquisition of 15 Selexis programs two years ago. Since then, many of the programs have advanced through the development process and Ligand has already received milestone payments amounting to nearly 10 percent of the acquisition price, according to the news release.