(Reuters) - U.S. drugmaker Amgen's ( AMGN ) shares jumped 13% to $316.26 premarket on Friday as the company teased encouraging data for its experimental obesity drug, igniting investor hopes but leaving Wall Street frustrated over a lack of details.

Amgen ( AMGN ), which is conducting mid-stage studies of its injectable drug MariTide, said that it was "confident in MariTide's differentiated profile and believe it will address important unmet medical needs."

The company expects to have data from the Phase 2 trial late this year and said it is planning "for a comprehensive Phase 3 program across multiple indications," including diabetes.

Investors late Thursday shrugged off a slight drop in the company's first-quarter adjusted profit and slightly-lower-than expected sales of drugs including arthritis treatment Enbrel and psoriasis therapy Otezla.

"Never Mind the Quarter - How 'Bout That MariTide Update?," Piper Sandler analyst Christopher Raymond wrote in a research note, calling the quarter "sort of ho hum."

Raymond said the company's comments about investing in manufacturing capacity for clinical and commercial supply were encouraging, but added "frustratingly, management provided little color as to exactly HOW this agent appears differentiated from currently approved GLP-1s."

Brokerage RBC cut its price target on Amgen's ( AMGN ) stock by $4 to $332 after the results.

MariTide, given by injection, joins a compound designed to activate the GLP-1 hormone associated with a feeling of fullness to an antibody that blocks activity of a different gut hormone, GIP, which has been linked to metabolic regulation.

Amgen's ( AMGN ) stock, part of the bluechip Dow Jones index, has risen 21% in the past 12 months but underperformed those of weight-loss market leaders Eli Lilly ( LLY ) and Novo Nordisk, which have risen about 75% and 54%, respectively.

Amgen ( AMGN ) shares trade 13.9 times their forward 12-month earnings estimates, versus a forward price-to-earnings ratio of 34.2 for Novo Nordisk and 48.49 for Eli Lilly ( LLY ).