May 27 (Reuters) - Eli Lilly ( LLY ) will buy privately

held SiteOne Therapeutics in a deal worth as much as $1 billion,

the companies said on Tuesday, giving the drugmaker access to an

experimental non-opioid pain medicine.

SiteOne's STC-004 belongs to a class of drugs, known as

Nav1.8 inhibitors, that targets the channels involved in

transmitting pain signals.

Vertex Pharmaceuticals' ( VRTX ) recently approved

non-opioid painkiller Journavx also belongs to the same class.

Under the terms of the agreement, SiteOne shareholders could

receive up to $1 billion in cash, inclusive of an upfront

payment and subsequent payments upon achievement of certain

regulatory and commercial milestones.