OraSure Technologies, best known for its rapid HIV tests, is purchasing UrSure Inc., a private Boston-based company that has developed tests to measure adherence to pre-exposure prophylaxis, or PrEP, the daily tablet taken by HIV-negative people to prevent contracting the virus.

OraSure will pay $3 million up front, according to a press release about the acquisition. An additional $28 million will be made available if and when specific development milestones are met.

A test to measure PrEP adherence is important because doctors depend on patient self-report to assess whether they’re taking the med, a method that is often unreliable. If doctors know which patients aren’t adhering to the daily regimen, they can apportion resources to help them. What’s more, as the UrSure video above explains, those who don’t stick with the routine are more likely to drop out of care.

UrSure was developed by two HIV doctors—Helen Koenig, MD, and Giffin Daughtridge, MD—who operated a PrEP clinic in Philadelphia. According to a profile on the company published in BostInno, which covers local business trends, the two doctors recognized the need to measure PrEP adherence when some clients who claimed to have taken the prevention med would later test positive for HIV.

UrSure has developed two versions of a urine test that measures levels of tenofovir, one of the two meds in PrEP. One is a lab-based test: Urine samples must be sent in, and the results are available in a few days. The other is a point-of-care test that health care can administer in their clinics.

“Our tests allow providers to objectively identify which of their patients need more adherence support rather than depend on self-report, which is notoriously unreliable,” Daughtridge, UrSure’s CEO, explained to BostInno. “With this information, they can then allocate resources like targeted counseling or a case manager to those individuals who are struggling with adherence. We are the only company in the world that has commercialized a PrEP adherence test, and we have a pipeline of additional medication adherence tests in development.”

Daughtridge and Koenig launched their company at Harvard University’s Innovation Lab and incorporated it in 2015 (read an interview with Daughtridge here). As of November, the start-up had sold more than 4,000 tests to clinics in 10 states, BostInno reports.

“The addition of UrSure to OraSure’s portfolio complements our work with HIV diagnostics and strengthens OraSure’s position as a global leader among public-health focused diagnostic companies in the HIV field,” OraSure’s president and CEO, Stephen Tang, PhD, said in the press release. “We are now able to offer a product line that covers the spectrum from screening to treatment adherence. We are proud that we are working to end the HIV/AIDS epidemic by helping people know their HIV status, remain adherent and reduce the risk of HIV transmission.”

Scientists estimate PrEP to be about 99% effective among men who have sex with men and greater than the current 88% to 90% estimate for heterosexual men and women. For more details, see the POZ article “How Well Do U=U and PrEP Work? The CDC Updates Its Answers.”

Both versions of PrEP currently approved by the Food and Drug Administration, Truvada and Descovy, consist of two meds (both include a version of tenofovir, the drug measured by UrSure), and both tablets are manufactured by Gilead Sciences. For more details, see “What’s the Difference Between Truvada and Descovy for PrEP?”

In related POZ news from this week, see “Why Are Only 891 People Enrolled in a Free PrEP Program for 200,000?” and “What Happens to PEP Prescribing During Lockdown?”