Celgene will invest $17m in the immuno-oncology company, also backed by Sorrento, as it floats in the largest biotech initial public offering ever.

NantKwest, the US-based immuno-oncology company formerly known as Conkwest, will raise $207m when it goes public later today, giving an exit to backers including Sorrento Pharmaceuticals.

NantKwest is issuing almost 8.3 million shares on Nadsaq priced at $25.00 each, above its $20 to $23 range. The price gives the company a market cap of $2.6bn, reportedly the largest ever for a biotechnology IPO.

Founded in 2002 as ZelleRx before changing its name to Conkwest, the company is developing immunotherapy drugs…