If there’s one thing most patients with sickle cell disease will agree on, it’s that sickle cell hurts. A lot.

The characteristic rigid, sticky, C-shaped red blood cells of this inherited disease tend to get stuck in the small blood vessels of the body. If so many get stuck in a vessel that they cut off blood flow, the body sends out a warning signal in the form of searing pain that doctors call a pain or vaso-occlusive crisis (at least, that’s the historic view; more on that in a minute). The pain can happen anywhere in the body, but most often occurs in the bones of the arms, legs, chest and spine.

Preventing flare-ups—and stopping them when they happen—is a major part of the care plan for any patient with sickle cell. Right now doctors try to avoid pain crises largely by diluting a patient’s blood with fluids or transfusions, thereby keeping the numbers of sickled cells relatively low.

What these treatments don’t do is tackle the pain directly. Doctors can use pain medications, but over time, patients can become tolerant to painkillers, requiring ever-larger doses. What’s needed is something that can stop the complex cascade of events that ignite a pain crisis. …