Vertex offers an incremental answer to a perennial question

As problems go, making more than $4 billion a year is a pretty decent one to have. Vertex Pharmaceuticals will soon have four approved medicines for cystic fibrosis, which add up to one of the most enviably lucrative portfolios in all of biotech. But, Wall Street being a what-have-you-done-for-me-lately kind of place, the Boston biotech is now facing a simple question: Then what?

Yesterday, we got an answer of sorts. Vertex agreed to pay $950 million for Semma Therapeutics, an early-stage startup trying to turn stem cells into a curative treatment for type 1 diabetes. The idea is to fashion insulin-producing beta cells that can replace the ones mistakenly destroyed by patients’ immune systems and, eventually, have them meted out by an implant that replicates the effects of a healthy pancreas.

Semma’s work is yet to be studied in humans and years away from becoming a product, but it fits alongside the company’s recent pipeline-expanding deals. So far this year, Vertex has invested in CRISPR genome editing and synthetic messenger RNA, unproven technologies that could have dramatic effects on serious disease.