** Shares of drug developer Acelyrin SLRN.O rise 17.05% to $2.54 premarket

** SLRN confirms that private affiliate of investor Tang Capital Partners, Concentra Biosciences, has proposed to acquire it for $3 per share in cash, a 38.2% premium to its last closing price

** The offer implies an equity value of about $300 million, according to Reuters calculations, plus a "contingent value right"

** The investor had a 5.3% stake in SLRN - filing

** Earlier this month, SLRN announced an agreement to merge with Alumis ALMS.O in an all-stock transaction

** SLRN shares have fallen nearly 38% since it reported mid-stage data from its thyroid eye disease drug in early January

(Reporting by Siddhi Mahatole)

((Siddhiprabhanjan.mahatole@thomsonreuters.com))