LONDON, Nov. 5 -- AstraZeneca's reported pursuit of Rhythm Pharmaceuticals would buy a foothold in rare forms of obesity, rather than an immediate challenger in the mass-market weight-loss business. The distinction matters to a proposed price of about $10 billion for a company whose latest quarterly product revenue was $92.1 million.

Reuters reported on November 4, citing three people familiar with the matter, that AstraZeneca had made a non-binding proposal worth as much as $134 a share, including payments tied to milestones. AstraZeneca declined to comment to Reuters, while Rhythm did not respond to the agency's request. Neither response establishes an agreed transaction.

The potential acquisition would run through Alexion, AstraZenec...