Adherence to PrEP, the HIV prevention drug, is low. A new study suggests a pill with a tiny sensor might help

With a daily pill, people who face an elevated risk of exposure to HIV can dramatically lower their chances of contracting the virus. But that protection is only effective if people adhere to a strict regimen with their prescription.

Many do not.

A solution, researchers say, may come in the form of a digital pill — one equipped with a sensor about the size of a grain of salt.

On Tuesday, researchers at the 22nd International AIDS Conference in Amsterdam presented data showing that such pills not only recorded exactly when patients were taking the medication but also delivered the drug as effectively as normal pills.

Smart pills are “a patient empowerment tool,” said Sara Browne, an associate professor of clinical medicine at the University of California, San Diego, who was involved with the study. “Everything is geared around the patient learning more about themselves.”

For people who share needles while using drugs or have HIV-positive partners, pre-exposure prophylaxis (PrEP) can reduce the chance of infection by more than 90 percent. Unfortunately many people forget to follow the guidelines for PrEP — a daily pill prescribed under the brand name Truvada — leaving them vulnerable to the virus. In some clinical trials, inconsistent use reduced the drug’s efficacy to zero percent.

“PrEP has had a very slow start to a really great impact,” said Jessica Haberer, an associate professor at Harvard Medical School and director of research for the Center of Global Health at Massachusetts General Hospital. “We know that [Truvada] works if you take it. The challenge has been in being able to [do so].”

The digital pills used in the PrEP study relay information across three devices: an FDA-approved ingestible sensor that is attached to the pill, a Band Aid-like patch worn on the upper torso, and a smartphone.

The sensor, made from silicon, magnesium, and copper, emits a faint electrical pulse when it contacts stomach acid. The signal, first recorded by the patch, is sent via Bluetooth to the patient’s phone. From there, the information is encrypted and uploaded to a secure server, where patients can check to see how well they have followed their medication schedule. The patch can also track when patients are resting or exercising, allowing for a more comprehensive view of their health.

“The patients own the data and the patients decide who they want to share the data with,” said Browne. With permission, doctors, family members, or friends could remind and encourage patients to keep taking Truvada.

Proteus Digital Health, the company that manufactures the sensors, is betting that smart pills will be an improvement on previous techniques used to determine whether patients have been taking their medication.

Clinical trials involving PrEP have proven challenging. To ensure participants are taking their daily doses, researchers have relied on time-consuming and costly tests that measure drug levels in blood or hair.

“A couple of these huge multimillion-dollar studies actually failed because people weren’t taking PrEP,” said Philip Chan, associate professor at Brown University and medical director of the PrEP program there, who was not associated with the study. “That’s what really started the conversations and concerns about people taking PrEP and the fact that you really need to take it for it to be effective.”

While blood and hair tests calculate the average dose of medication taken over a few weeks or months, they lack the daily precision of an ingestible sensor. “When someone knows they have an appointment coming up, they can take [more of] the drug three of four days before they come in,” said Browne. Without a smart pill, “it can be difficult to understand how comprehensively people have been taking their medication and how well they are really doing.”

In real-world settings with more limited time and resources, doctors rely on patients to report any lapses in treatment. According to Chan, these lapses occur have several causes. In some cases, patients simply forget to take their medication for everyday reasons: they get caught up with work or go on vacation. In others cases, people at high risk of contracting HIV may also be struggling with substance abuse and depression. For these patients especially, smart pills could help overcome mental barriers to treatment.

Digital Truvada enables a “really positive, personalized adherence tracking,” said Haberer, who was not associated with the study. If patients miss certain days, doctors can look for patterns during counseling sessions: Was substance abuse a factor, or were others issues, like a patient’s whereabouts.

A smart pill — like a Fitbit for exercise enthusiasts trying to stick to a routine — could also enable patients to better understand what influences helped them take their medication on time.

These technologies are “helping us understand who we are, what are our bodies doing,” said Haberer, “and then using that feedback to modify our behavior.”

Before digital Truvada is widely adopted, Proteus and Gilead, the company that produces Truvada, must address concerns with privacy and cost. Although data from the sensor are encrypted in the same way as bank transactions, patients may still be wary of uploading information or feel coerced into sharing data with others.

Emily Largent, an assistant professor at the Perelman School of Medicine at the University of Pennsylvania who was not involved with the study, said she worries that insurance companies may decide to cover digital Truvada only if patients grant access to their data. Under such “conditional coverage,” she said, using the medication would not be “as voluntary as we might like.”

The cost of a smart pill depends on many factors including manufacturing practices. Proteus has been selling stand-alone digital pills and patches since 2012, but just last year gained FDA approval to merge its technology into the antipsychotic medication Abilify. Unlike the gelatin encapsulation used to encase Truvada and the sensor, Abilify MyCite was manufactured by embedding the sensor directly into the pill, a strategy that reduces the cost of the medication.

Digital Truvada “may not be worth the investment for everyone,” said Haberer. “But for people who really value [personalized] information, I think it can be a really nice intervention and something that we should be exploring.”