It was another busy week for pharmaceutical deals, but Alexion (NASDAQ: ALXN) took the prize for biggest deal with its $8.4 billion acquisition of Synageva BioPharma Corp., a privately held pharma company specializing in treatments for rare diseases. Alexion touted the fact that Synageva’s pipeline complements its own and the combined company will be one of the most robust rare disease pipelines, with more than 30 diverse pre-clinical programs. The price consists of $115 in cash and 0.6581 ALXN shares for each share of Synageva, implying a total per-share value of $230, based on the nine-day volume-weighted average closing price of Alexion stock through May 5, 2015.