Cambridge’s Aveo Pharmaceuticals Inc. rose on its offering of 6.7 million shares for $7.50 each. The company said it expects to raise about $50 million before discounts and commissions. The offering is expected to close on Wednesday. Aveo helped develop an experimental cancer pill — Tivopath — that is currently under review by the Food and Drug Administration to treat advanced kidney cancer. The agency is expected to finish its review by July.