Precision medicine: Precision medicine is a strategy for using gene sequencing tests and related tests to determine what kinds of treatments might help a patient the most.

Genes are chains of nucleotides, or molecules, inside living organisms' cells. Cells use genes to store the information they need to make new cells, eat, breathe and talk to other cells.

Until recently, identifying which nucleotides sat where on people's genes was difficult, slow and expensive. Many of the patients in early precision medicine programs suffered from aggressive forms of cancer or other dire conditions that justified the high cost of genetic testing.

Now, the cost of gene sequencing technology is falling, the scope of precision medicine research is growing, and doctors are using precision medicine strategies to treat a wider range of conditions.

Precision medicine for obesity: Phenomix is a Menlo Park, California-based company that draws on obesity research conducted by Dr. Andres Acosta and other scientists at the Mayo Clinic.

The researchers collected saliva samples from people with obesity, analyzed the DNA in the saliva, and used the results and other patient information to divide the people into four main "phenotypes," or groups:

• People who eat too much because of their emotions.
• People who really do metabolize food slowly.
• People with brains that are inclined to feel hungry.
• People with guts that send out hunger signals quickly because the guts empty quickly.

Acosta was part of another team that reported earlier this year on the results of a study that divided 84 people with obesity based on whether they fit in the hungry gut category, based on genes and other indicators. Obese people with the hungry gut type who took semaglutide, the active ingredient in Wegovy, lost about 20% of their initial weight after 12 months, while people without the hungry gut trait who took semaglutide lost just 10% of their weight, the researchers found.

The new program: InformedDNA genetic counselors will start by helping a patient send in a saliva sample. Phenomix will analyze the genes in the sample. The companies will then describe the factors that they think are contributing to the patient's obesity.

Counselors can then make recommendations about lifestyle changes, food choices and medications that might fit with the patient's obesity type.

Payers: Mark Bagnall, the CEO of Phenomix Sciences, said via email that persuading health plans to pay for obesity care and precision medicine gene tests has always been a challenge.

But the picture is now somewhat different for precision medicine programs that can help plans decide which patients need GLP-1 agonists the most.

"Payers are keenly interested in understanding who will be the responders to the medication and who will not," Bagnall said.

Dr. Surya Singh, the CEO of InformedDNA, which is based in St. Petersburg, Florida, said payers seem to be warming up to the idea of applying precision medicine strategies to conditions other than cancer.

"Pharmacogenomics (testing for genomically-driven variation in drug responsiveness) has emerged as an important tool in additional areas such as behavioral health, neurology, and cardiac disease," Singh said. "Many plans cover tests in these areas also. This is absolutely a moving target, now more than ever."

About 20 states have helped gene testing programs by enacting "biomarker bills" that require Medicaid plans and commercial plans to cover gene sequencing, Singh said.