Pfizer (PFE), one of the world's biggest pharmaceutical firms, may have had a $106 billion takeover bid for British drug maker AstraZeneca (London Stock Exchange: AZN-GB) rejected, but analysts expect it to get its way in the end.

They give these reasons for that conclusion: Pfizer probably has more room to raise its offer and win over AstraZeneca shareholders, a rival bid for the British firm is unlikely, the deal is unlikely to face any major regulatory hurdles and a weak earnings backdrop is an incentive for Pfizer to push for a deal now.

Read More Pfizer $106.5 B offer 'inadequate': AstraZeneca

"Pfizer has historically been aggressive at pursing mega-mergers when it considers it the right time," Raghuram Selvaraju, head of healthcare equity research at Aegis (:AEGSF) Capital, told CNBC Asia's "Run Down."

"We think this upcoming merger with AstraZeneca could be Pfizer's easiest takeover yet, mainly because it is primarily motivated by taxes and Pfizer is trying to escape U.S. taxes and get into the U.K. tax system which will yield significant profits for shareholders form the combined companies," he said.

According to Selvaraju, Pfizer currently has a tax rate of about 27 percent in the U.S. and it would pay a rate of about 10 percent on profits generated on UK-based patents.

"Pfizer won't reveal what the blended tax rate would be but obviously we can expect it to be below the 27 percent it currently pays," Selvaraju said.

Pfizer on Friday raised its initial cash and stock offer to just over $106 billion from $99 billion in its third attempt to win over AstraZeneca. AstraZeneca's board rejected the latest bid just hours after it was received, saying the offer was too low.

Read More UK politicians weigh in on Pfizer's AstraZeneca bid

Selvaraju said he expects that Pfizer could probably up its offer to the $110-120 billion range without any serious problem.

If the merger goes through, it would be the largest acquisition of a British company by a foreign business.

Incentive

Pfizer on Monday said its total first-quarter revenue fell 9 percent to $11.35 billion, which was $730 million below Wall Street expectations, on falling sales for generic drugs and highlighting its interest to pursue AstraZeneca to promote business growth.

Read More Pfizer sales way off mark as company pursues AstraZeneca

"We are rather skeptical about the company's optimism that all is going well. And we consider the bid for AstraZeneca as plan B rather than plan A," Sam Isaly, founder and managing partner at OrbiMed Advisors, which holds shares in Pfizer, told CNBC's "Fast Money."