DRUGS firm AstraZeneca saw as much as £1.5bn wiped off its share price after US rival Pfizer ended its £69bn takeover offer.
Shares in the pharmaceuticals company fell as much as three per cent as traders reacted to Viagra maker' Pfizer's decision to end its bid.
It meant the market value of the firm was £16bn less than what Pfizer had been prepared to pay.
The US company's chief executive Ian Read said the rejection of its £55-per-share final offer was a missed opportunity for the UK and Astra's shareholders.
Pfizer pulled out just before a 28-day takeover time frame expired, despite the urgings of some AstraZeneca shareholders that it should continue talks.
AstraZeneca chairman Leif Johansson said: "We welcome the opportunity to continue building on the momentum we have already demonstrated as an independent company.
"In the coming months, we anticipate positive news across our core therapeutic areas, which underpins our confidence in the long-term prospects of the business."
Investors were divided over whether AstraZeneca would be worth more as a standalone business producing its pipeline of drugs, or whether they should accept Pfizer's offer of cash and shares now.
Neil Woodford, the high-profile UK fund manager and a long-term AstraZeneca investor, said: "I applaud the board's resolute resistance of the Pfizer approach, based on their long-term value judgment that I fully support.
"I remain convinced that an independent AstraZeneca will achieve far better returns for its shareholders than the combination of cash and Pfizer paper would have delivered."
However, a number of other significant investors said Astra should have kept talking to Pfizer.
Last week Legal & General, which owns a 3.5 per cent stake in AstraZeneca, had reportedly written to the board asking it to engage in talks with Pfizer.
Also, Schroders, which owns a two per cent chunk of the UK firm, had expressed disappointment at the quick rejection of Pfizer's offer as well as the US firm's decision to call its £55 offer final - limiting any further room for manoeuvre.