FIVE life-size figures lie upon the gallery floor. They are white, naked and waxen, and seem to hang as if weightless, gently suspended in pools of spotlights.

This sense of suspension captures the mood of Chemical Life Support, Marc Quinn’s latest show, which, by looking at dependency, explores the balance between life and death. The sculpted figures are portraits of real people who suffer from chronic disease, and the exact dosage of the drugs that keep them alive for one day have been mixed in with the polymer wax from which their effigies have been cast.

The slender woman who lies there like a sylph trapped in flight is Silvia Petretti, who is HIV positive, and the sculpture includes her antiviral medicines. The powerfully built man is Carl Whittaker, an athlete who had a heart transplant and needs drugs to prevent rejection. At the centre of the space lies an image of Quinn’s son, Lucas, who is allergic to milk. His portrait, Innoscience, includes a chemically mixed powder substitute.

Quinn looks at the fragile miracle of life. In one sense, his figures, presented in poses adopted in sleep, look so vulnerable, so tender, so naked, so exposed. You see the wrinkles on upturned soles of feet, the soft defenceless skin at the backs of the knees, the fingertips stretched unfeeling into emptiness. In another sense, they look so strong. When the subjects were sleeping, their positions were propped up by pillows and chairs. Without the accompanying bedding, however, some of the casts seem almost frozen in a struggle of activity. You see the awkwardness of elbows, the bunching of musculature, the arch of a spine.

Half dead, half alive, half sleeping, half waking, half sculpted, half real, the figures are, in their poses, echoes of Bernini, of Michelangelo’s The Dying Slave, of a Bellini Christ child. Quinn extends the investigation of themes he tackled in earlier pieces, such as his famous “blood head”, or in his marble sculptures of amputees that (not least when displayed at the Victoria and Albert Museum alongside The Three Graces) set ideal against real and questioned expectations of beauty. In these new pieces, the people look healthy, but without their drugs they would die. They are plugged into the life-support machine of medicine.

The benefits of science are celebrated but, in an upstairs gallery, a dark side is shown. Innocence gives way to corruption. A skinned and eviscerated rabbit carcass, digitally scanned and computer enlarged, has been cast in bronze. Like some terrible abortion of Rodin’s Balzac, it lowers.

I could not help but think of those fearful lines of Yeats: “And what rough beast, its hour come round at last/ Slouches towards Bethlehem to be born?” This is the work that makes the show worth the trip. Of all the artists who came to fame with the label YBA, Quinn is the one who continues to combine powerful visual impact with careful thought.

Chemical Life Support is at White Cube, 020-7930 5373, until April 9.