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JHU Researchers Develop 15-Minute PCR System, Drug-Resistant Gonorrhea Test

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NEW YORK – A research team at Johns Hopkins University has created a point-of-care diagnostic system that can perform sample-to-answer infectious disease assays in 15 minutes. The device is the newest generation of an ongoing diagnostic device development project, and the JHU team now plans to commercialize it through a spinout company.

Called portable, rapid, on-cartridge magnetofluidic purification and testing, or PROMPT, the device is currently being developed along with an assay to detect drug-resistant gonorrhea infections directly from male swab samples.

Tza-Huei Wang has led the device's development from his lab in the JHU's Institute for NanoBiotechnology.

Compared to versions described previously, the newest generation of the system incorporates sample preparation, uses true PCR as opposed to isothermal amplification, and has revved the time to results from 50 minutes to 15 minutes, Wang said in an interview

In terms of taking the next step to commercialization, "We feel we are ready now," he said.

Initial versions of the system incorporated portable isothermal amplification and a smartphone reader to detect chlamydia infections. It used a magnetofluidic approach the team has developed that relies on magnetic particles to sequester the amplification reaction near the walls of a thin reaction vessel.

The team soon debuted a second generation system that incorporated true PCR and a droplet magnetofluidics device cartridge. That system was demoed with a test to detect hepatitis C virus in 50 minutes.

The new, third generation version of the system, however, has substantially shortened the time to results, a feat which Wang said has been made possible by new engineering, materials, and cartridge design.

"We are able to do 40-cycle PCR in 12 minutes, plus three minutes of sample preparation and DNA extraction," he said.

In the rapid point-of-care diagnostics space, this speed is on par with, or faster than, many other systems. It could potentially be more sensitive than those that rely on isothermal amplification, and it could be faster than isothermal, as well.

After one minute of hands-on time, this instrument then automatically performs sample prep, thermal cycling, and readout. Test results are reported via a smartphone app, rather than on a screen on the instrument.

Wang said the rapid thermal cycling is enabled by the magnetofluidic approach, which effectively decreases the thermal mass of the reaction.

Localized heating — which is a technique similar to one used by GNA Biosolutions, for example — has the advantage of obviating the need for pumps to move sample about in a cartridge, thereby decreasing complexity and manufacturing costs.

The system also uses high concentrations of primer and enzymes to maximize the reaction kinetics.

While there are a few rapid, handheld, true PCR sample-to-answer systems with fluorescence detection in development, most systems that have been commercialized — like the Bosch Vivalytic or QuantumDx Q-POC, for example — are benchtop instruments like PROMPT, or have separate handheld and benchtop components.

But the PROMPT instrument is quite small among rapid, point-of-care, true PCR systems, being only 12.7 centimeters tall, 13.4 centimeters deep, and 8.4 centimeters wide.

The cartridges, in particular, were designed to be inexpensive to manufacture, Wang said, so that it can be useful in low-resource settings. The cartridges themselves use a combination of molded plastic and laser cut plastic layers, and the cost per cartridge, including thermoplastics and assay reagents, is $2.09. 

Wang said the PROMPT technology is patented, and his team is now acquiring the license from JHU in order to spin out a company with a commercialization timeline of two to three years.

"We are predicting an aggressive timeline because of the maturity of this technology," he said.

He and his colleagues have also obtained translational funding from the Maryland Innovation Initiative and will apply for additional support to bring the system into a commercial product.

Gonorrhea resistance

For a study evaluating PROMPT's gonorrhea assay published this month in Science Translational Medicine, the JHU team partnered with long-time partners at a local clinic focused on sexually transmitted infections in Baltimore and at a clinic in Kampala, Uganda.

These sites used the assay that can detect gonorrhea pathogens as well as a particular type of drug resistance to test samples from 252 patients, and surveyed clinicians and lab technicians about the system.

They found an overall sensitivities and specificities of approximately 98 percent compared to lab-based PCR testing, and a 100 percent concordance of the resistance call with culture-based results.

At the Uganda site in particular, the team found clinicians feel time is critical in the clinical workflow, as wait times for results were a major hurdle to getting patients treated. And, approximately 90 percent of clinicians surveyed at the Uganda site said they found the PROMPT test to be easy to use, according to the study.

Gonorrhea "superbugs" have been a growing concern worldwide for a few years, and Wang noted that the US Centers for Disease Control updated its gonorrhea treatment guidelines in December 2020.

The agency had previously recommended azithromycin and a drug called ceftriaxone as a first-line treatment, but now recommends ceftriaxone as a monotherapy — in the form of a single intramuscular injection — for all gonorrhea infections because of increasing rates of azithromycin resistance.

An older antibiotic called ciprofloxacin, or cipro, had been used more rarely for a few decades because of resistance. Surveillance data from the Gonococcal Isolate Surveillance Project indicate that the prevalence of cipro resistance is around 20 percent in the US, but because cipro is less expensive and easier to use than ceftriaxone, prescribing it for the 80 percent of infections that are susceptible could have benefits, including slowing down the development of ceftriaxone resistant gonorrhea.

The JHU gonorrhea test specifically detects the cipro resistance-conferring mutation in serine 91 of the gyrA gene.

POC STI MDx

PROMPT's clinical validation was supported by the Point of Care Technologies Research Network, or POCTRN, site at JHU.

Charlotte Gaydos, a point-of-care STI diagnostic researcher at JHU and lead of JHU's POCTRN site, worked with Wang's team and is a co-author on the STM study. In an email, she noted that Binx Health's Binx io system would be an example of the typical 10-year timeline for a startup to commercialize a point-of-care STI diagnostic device. A similar timeline is exemplified by Talis Biomedical.

But it appears the timeline to take a technology from the lab to a commercial product has been dramatically accelerated by the pandemic, in part through the efforts and collaboration of longtime supporters POCTRN and Rapid Acceleration of Diagnostics, or RADx program at the US National Institutes of Health.

In Gaydos' estimation, a two- to three-year commercialization timeline for PROMPT is reasonable.

Overall, the future of rapid point-of-care STI testing seems more dynamic than before the pandemic.

In addition to providing early support to Binx, JHU's arm of the POCTRN program also supported firms like Novel Microdevices, a firm that was recently granted up to $13.8 million in milestone-based funding from the Combating Antibiotic Resistant Bacteria Biopharmaceutical Accelerator, or CARB-X. Other firms are also homing in on gonorrhea resistance. SpeeDx has partnered with QuantumDx to port that firm's gonorrhea superbug tests to the Q-POC and was recently awarded up to $3.7 million from CARB-X.

Still, Gaydos said she doesn't believe there will be competition for point-of-care STI testing in the future because the market is quite large and every person and clinic has different needs. "Different strokes for different folks," she said.

She also believes these STI tests will absolutely be available over the counter someday.

The Emergency Use Authorized SARS-CoV-2 test from Visby Medical is an example of what at-home users may soon see at the pharmacy. "It does not require a separate machine to do the test and could eventually be OTC," Gaydos said, emphasizing, "The platform for doing and reading the test is contained in the cartridge, which is about the size of a deck of cards."

In the meantime, Wang said his team is currently working to make PROMPT even faster. They are also continuing to develop a sepsis test with melt curve detection.

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