(Bloomberg) -- AstraZeneca Plc has become the first British company to be valued at more than £200 billion ($257 billion) after a big bet on cancer drugs helped drive a rally in the shares.

Shares climbed as much as 0.5% on Wednesday, extending an advance this year to 22%. The firm’s market value closed above £200 billion for the first time on Tuesday.

AstraZeneca is the UK’s most valuable listed company, having kept a lead over Shell Plc since April, and is ranked seventh in Europe by market value in dollar terms.

“Its growth has been steady rather than showy, with the potential for advances in cancer treatment, and in some cases weight-loss drugs, attracting investor attention,” said Danni Hewson, head of financial analysis at AJ Bell. “It’s also a boon for London markets, which have been fighting to maintain their relevance.”

Chief Executive Officer Pascal Soriot, who has been at the helm of AstraZeneca since 2012, has won plaudits for boosting the stock price following Pfizer Inc.’s failed takeover attempt two years into his reign. His bet on cancer drugs lifted annual revenue to more than $45 billion by 2023 and he is looking to cement his legacy with a further near-doubling of sales by 2030.