Bristol-Myers Squibb shareholders are not happy with the company's plan to purchase a smaller rival, sending the larger company's shares down twelve percent at the end of the day on Wall Street.

Conversely, shares of New Jersey-based cancer drug maker Celgene surged 25 percent after the deal was announced.  New York-based Bristol wants to purchase Celgene in a cash and stock deal valued at US$74 Billion.  Celgene shareholders will receive one Bristol-Myers Squibb share and $50 in cash for each Celgene share held.  But once the debt is factored in, the value of the deal balloons to about $95 Billion, which would make it the largest health-care deal on record.

That price tag - 50 percent above Celgene's market worth before the announcement - may be too high for Bristol's large institutional shareholders, some of which already seemed poised to throw a spanner in the works by voting against the deal.  The deal would also be subject to various regulatory approvals.

Absorbing Celgene would give Bristol a boost to its immuno-oncology portfolio as it struggles to keep up with rival Merck Pharmaceuticals.  The combined firm would havenine medicines that each generate more than US$1 Billion in annual sales, plus a broad field of drugs in development that could result in $15 Billion in revenue.

"This deal is really all about the launches," said Bristol chief executive Giovanni Caforio.  "Given the number of short-term launches and growth opportunities, we believe this is the right time."