Concert Pharmaceuticals makes drugs better--literally. The Lexington, Massachusetts–based company takes existing pharmaceuticals and replaces their hydrogen atoms with an isotope called deuterium. The purpose? The heavier deuterium appears to give the medication an effectiveness boost and to reduce side effects, allowing it to stay longer in the patient's system while maintaining its disease-fighting purpose.

Following through has required patience from CEO Roger Tung, who founded Concert in 2006: While clinical trials on a number of drugs have shown promise, the company is still waiting for its first FDA home run. It takes more than a decade, on average, for a medication to go from inception to market--and fewer than one out of 10 makes the final cut. "There are very few businesses as capital intensive and as long to get to product as pharmaceuticals," Tung says. In the meantime, Concert brings in bucks via licensing agreements with other drug companies. Vertex Pharma­ceuticals, for example, recently paid Concert $160 million for the right to take over a cystic fibrosis drug called CTP-656. Tung says his company will use the money to move forward with a treatment for alopecia areata, an autoimmune disease that causes hair loss. --Helaine Olen

This San Carlos, California-based biotech company makes non-invasive prenatal tests. Co-founder and CEO Matthew Rabinowitz saw his family devastated by the death of a baby with an untested genetic condition; he founded Natera to develop tests that can pick up on fetal chromosomal issues nine weeks into pregnancy. Natera's flagship test, known as an NIPT, analyzes traces of fetal cells that circulate in the mother's blood. Rabinowitz is tapping into a $665 million-plus global market of non-invasive prenatal testing, according to Persistence Market Research, and expanding: Natera hopes to unveil cancer diagnostics by the end of this year.

San Francisco-based Twilio already provides the cloud-communications backbone for some 36,000 customers, including Coca-Cola and Nordstrom. Its technology lets you message with your Uber driver, reminds you about appointments, and helps you generate passwords. Now it's expanding its capabilities--and mediums, especially into video. For example, telemedicine provider Doctor on Demand uses Twilio to connect doctors and patients via videoconferencing. "Voice and messaging are the biggest parts of our business, but video is coming on incredibly strong," says Patrick Malatack, Twilio's VP of product. --Kate Rockwood

Xenon Pharmaceuticals tries to help humans get better, from the genes up. The Burnaby, British Columbia–based company, co-founded by CEO Simon Pimstone in 1996, uses a proprietary platform to develop potential gene therapies for conditions ranging from epilepsy to pimples. It's an ambitious, sometimes frustrating mandate--the company recently killed its acne treatment after two years of tests--but Xenon's innovations remain in high demand from pharma peers like Teva and Genentech, for which Xenon is developing pain-relief drugs. --Helaine Olen