Gamaleya's vaccine is a so-called viral vector vaccine, meaning it employs another virus to carry the DNA encoding of the needed immune response into cells.
The companies did not disclose the financial details of the agreement, but said terms were based on the volume of doses and the timing of the delivery.
The Hang Seng index fell 0.7pc, to 24,710.59 points, while the China Enterprises Index, which tracks Hong Kong-listed Chinese firms, lost 0.9pc, to 10,097.08 points.
Positive COVID-19 vaccine developments, with Moderna Inc and Pfizer Inc launching two late-stage vaccines trials that could achieve regulatory approval and widespread use by end-2020.