Vertex just laid claim to an asset that might be very valuable.Biotech acquisitions continue to abound this year. On April 10, Vertex Pharmaceuticals (VRTX -0.92%) announced it would purchase Alpine Immune Sciences (ALPN -0.05%) for $4.9 billion in cash in a deal that's set to close before the end of this quarter. The prized asset that Vertex will gain as part of this purchase is ALPN-303, a potential autoimmune treatment that's in phase 2 clinical trials.But there's a lot more to the deal's potential value ...