In September, a biotech company started up in San Francisco with a goal of using a novel genomics-based approach to developing drugs for cardiomyopathy, a life-threatening heart condition that affects 60 million people worldwide. The company, called MyoKardia, is going after people who have genetic mutations that cause some forms of the condition, planning to market its drugs alongside diagnostic tests that identify the patients most likely to respond. Boston-based venture capital firm Third Rock Ventures launched MyoKardia with a $38 million investment.

MyoKardia scientists are developing drugs that address a subset of mutations in the sarcomere, the basic unit of heart muscle. Third Rock partner Charles Homcy, the company’s interim CEO, says scientists now understand mutations well enough to “match the genotype to the phenotype,” or the individual’s genetic mutations to the specific characteristics of his or her disease. MyoKardia is developing drugs that will be targeted to patients on the basis of both genotypes and phenotypes, he says.

Some cardiologists say they would welcome a more targeted approach to treating cardiomyopathy. “Several mutations have been found, but we don’t know exactly how they work, and we do not know how to treat them,” says Daphne Hsu, chief of pediatric cardiology at Montefiore Medical Center in New York. “All we can do now is treat symptoms. If genetics could lead to better therapies, that would be wonderful.”

MyoKardia is among a growing number of companies aiming to bring genomic testing into everyday clinical practice as the plummeting cost of gene sequencing makes such applications feasible. Last year, Ambry Genetics in Aliso Viejo, California, became one of the first diagnostics labs to offer a test that examines the protein-coding regions of all 20,000 genes in the human genome. Customers, who are typically physicians, can examine 4,000 genes that have been tied to specific diseases, or they can order a map of a patient’s entire genome.

Foundation Medicine, founded two years ago in Boston, is generating demand from big pharma for its technology, which can match specific genetic traits in individuals’ tumors with the medicines most likely to work. Novartis and Celgene have both formed collaborations with Foundation to use its technology in trials of new cancer drugs.

San Diego-based Illumina, which markets a range of genomic tools, announced in September that it is also answering the call for tests that can identify disease-causing genes. The company rolled out five products that evaluate genes associated with autism, cancer, cardiomyopathy, inherited pediatric diseases, and rare genetic diseases. Illumina is marketing them only to labs that want to develop their own sequencing tests, though the company says it intends to develop the product line, called TruSight, for clinical diagnostic use.

Will all this genetic testing be good for patients? “That’s the million-dollar question,” says Brenda Finucane, president of the National Society of Genetic Counselors. “It may be that certain genes confer a slightly increased risk of disease, but do we really have enough evidence to validate those genes? The verdict is still out.”

MyoKardia’s Homcy acknowledges that some patients with genetic mutations for cardiomyopathy don’t have symptoms, and it’s still not well understood how external factors like diet, environment, and other health conditions play into a person’s risk of advancing to full-blown heart failure. So MyoKardia’s second goal, he says, is to create a registry of cardiomyopathy patients so scientists can begin to answer those questions.