Liquid Sky (1982)

Invisible aliens in a tiny flying saucer come to Earth looking for heroin. They land on top of a New York apartment inhabited by a drug dealer and her androgynous, bisexual nymphomaniac lover, who's also a fashion model. The aliens soon find the human pheromones created in the brain during orgasm preferable to heroin, and the model's casual sex partners begin disappearing. This increasingly bizarre scenario's observed by a lonely woman in the building across the street, a German scientist who's following the aliens, and an equally androgynous, drug-addicted male model (both models are played by Anne Carlisle). Darkly funny and thoroughly weird.