“For the last several years I’ve been working on a book about how we’ve treated genetic diseases over the decades and why it’s been such a challenge. I’m focusing on a rare inherited metabolic disorder called “maple syrup urine disease.” It has that unfortunate name because affected patients’ urine emits a peculiar, sweet odor shortly after birth (for years this scent was the quickest path to diagnosis).”

“People with MSUD inherit two copies of a broken gene that leaves them unable to metabolize certain amino acids. Until the 1960s, they would die in infancy. But then researchers figured out how to keep them alive with nasty-tasting low-protein dietary formula. Later, some smart physicians and food scientists made the formulas both better-tasting and more nutritious.”

“And then in the early 2000s, we learned essentially by accident that a liver transplant would allow MSUD patients to eat a regular diet. But of course, liver transplants are expensive and carry their own risks, not least of which is a lifetime on immunosuppressive drugs. Now we’re on the cusp of gene therapy, which could potentially cure the disease. But even though the science is up to the task, the market is not: pharma companies don’t want to invest in one-and-done treatments for diseases that only affect, at most, a few hundred people a year.”

“For me the book is really taking this one disease as a lens through which to understand both the remarkable scientific progress we’ve made but also all of the remaining technical and policy challenges. It is both a celebration and an indictment of genetic medicine.”