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NephroSant Readies Launch of Kidney Transplant Rejection Assay


NEW YORK – Following the completion of a $16 million Series A financing round earlier this week, startup NephroSant now expects to launch its Qsant kidney transplant rejection prediction assay as a laboratory-developed test (LDT) at selected sites this spring.

The firm will also use the funding to develop updated versions of the assay that will include additional biomarkers for different disease indications.

NephroSant was initially launched in 2017 as a spinout from the University of California, San Francisco as KIT Bio before rebranding in 2019 and had originally planned to launch its test last year. Minnie Sarwal, NephroSant cofounder and UCSF professor of surgery, said that the firm has signed agreements with undisclosed commercial groups and kidney transplant registries across the US that will serve as its initial customers.

"We are deliberately rolling the test out to fewer sites initially before we expand nationally by the end of the year," Sarwal said. "We will work with tertiary transplant programs and key opinion leaders who understand the accuracy and clinical utility of the assay for proactive patient management."

The test, renamed "Qsant" from "Qisant" for easier pronunciation, analyzes six biomarkers from 4 ml of a patient's urine sample: the protein clusterin, the metabolite creatinine, the amount of cell-free DNA (cfDNA), the fraction of methylated cfDNA, the inflammation marker CXCL10, and the amount of total protein.

Qsant uses these measurements, which include a proprietary method for measuring cfDNA in urine, to generate a composite urine score (Q score) ranging from 1 to 100 to detect acute renal transplant rejection and estimate rejection risk.

After a transplant center orders the Qsant LDT, NephroSant sends a collection kit to the patient's home. The patient then returns the kit to NephroSant's CLIA-certified, CAP-accredited lab in San Francisco, where the firm's technicians run the Qsant assay. Nephrosant then sends a report to the transplant center, which includes scores for kidney transplant rejection risk and the intensity of rejection.

Once a sample arrives at NephroSant's lab in San Francisco, Sarwal said, the Qsant assay can produce a report in two to three days.

In 2020, Sarwal's team published research on the development and clinical validation of Qsant, as well as its sensitivity and specificity for the routine monitoring of renal allograft status. Last March, it described the initial performance of the assay in a study published in Science Translational Medicine. In a study published last July in the Journal of Clinical Medicine, the group found that the test had a sensitivity of 96 percent and specificity of 99 percent using a Q composite cutoff score of 32 (which Sarwal said maximizes the two values). She also noted that the firm has completed prospective trials, results of which it expects to publish in 2022.

In addition to predicting kidney transplant rejection several months before conventional methods, which involve extracting transplanted kidney samples every few months post-transplant and measuring serum creatinine levels, Sarwal highlighted Qsant's ability to measure the recovery or response to treatment such as immunosuppression. While NephroSant is currently in conversations with pharmaceutical firms to use the test for monitoring drug response, she declined to disclose potential partners at this time.

"Qsant correlates well with the amount of inflammation in tubulitis in the allograft, so we receive this accurate readout to the kind of treatment we're going to give the patient for the rejection episode," Sarwal said. "This is going to be a huge game changer because we don't have anything else in the space that gives us that granularity in the recovery of tubulitis in the kidney."

However, Sarwal acknowledged that one of the test's major limitations is the degradation of biomarkers in a patient's urine sample prior to analysis. Her team has filed a patent for a preservative solution that she said can be added to the urine sample to help tolerate up to five days of shipping at room temperature before degradation sets in.

The new funding will allow the company to develop its assay further. Sarwal noted that NephroSant began discussions with DaVita Venture, the venture arm of kidney care provider DaVita, about a funding round last June, eventually closing the Series A round by the end of the year. She said the firm waited to announce the closing of the funding until this week to "create momentum closely aligned to the launch of Qsant."

In addition to DaVita and current investors like DigitalDx Ventures, undisclosed angel investors participated in the round, and the firm has raised about $23.5 million so far since its 2017 launch.

"DaVita has typically operated at the end of the kidney disease space, including offering dialysis services," Sarwal said. "We believe [DaVita] is interested in working with us because they [want to] play a role in the entire spectrum of kidney disease management."

Sarwal envisions partnering with DaVita on other business opportunities related to the Qsant assay as part of the firm's plans to widen its reach in the organ transplant community. She believes that DaVita may also help NephroSant develop updated versions of the Qsant assay, which will add more biomarkers linked to other, undisclosed disease indications.

Commercial landscape

As NephroSant prepares to launch the Qsant assay this year, other firms are already vying for leadership in the liquid biopsy-based kidney transplant rejection monitoring space. Natera currently offers its Prospera kidney transplant assessment assay, which analyzes more than 13,000 single nucleotide polymorphisms (SNPs) to identify the percentage of donor-derived cfDNA (dd-cfDNA) in a transplant recipient's blood sample. The test can be used in cases when a physician believes that a patient needs to be tested for rejection and the risk/benefit profile of the test is superior to that of a biopsy.


CareDx offers a similar assay called AlloSure, which also analyzes SNPs in a patient's blood sample to detect dd-cfDNA for organ transplant rejection.

Both firms are engaged in an ongoing legal battle over intellectual property infringement and false advertising regarding the two assays.


Swedish startup Devyser, meanwhile, is developing a next-generation sequencing assay to detect kidney transplant rejection. Its test will analyze dd-cfDNA in the bloodstream stemming from kidney tissue damage.

Sarwal said that NephroSant stands out from competitors by analyzing multiple different biomarkers – not just cfDNA — and offering a noninvasive option for patients via collection of urine instead of blood. The firm will market the Qsant test directly to kidney transplant clinicians and their patients as an alternative to blood-based monitoring options that require phlebotomy.

Sarwal also argued that the firm provides patients the option of sample collection "within the safety and convenience of their own home, especially during COVID-19."

"The Q score generated does not only distinguish rejection from no rejection, but also provides a quantitative measure of transplant rejection risk, which correlates with rejection injury parameters in the biopsy," Sarwal said. "We anticipate that the convenience of sampling, the increased safety to the patient, the accuracy of the test, and its correlation with histological parameters of rejection injury, will all help NephroSant gain market share."

NephroSant is currently awaiting coverage decisions from the Centers for Medicare and Medicaid for the Qsant test. While the firm will offer Qsant as a registry-based test, Sarwal declined to provide an estimated price for the assay.

"Transplant monitoring is a very strong value add, because you're trying to minimize the costs related to hospitalization and unnecessary immunosuppression, which causes infections and cancer," Sarwal said. "Reimbursement will be [set] by Medicare, as about 80 percent of our transplant patients are covered by Medicare."

Once NephroSant receives CMS reimbursement for the assay, Sarwal said, the firm will begin discussions with private payors.

Research pipeline

While NephroSant will use most of the round's funds to launch Qsant and develop additional versions of the test, Sarwal said her team will also explore the potential for monitoring other solid organ transplant recipients for kidney damage, which can be caused by exposure to immunosuppressive drugs.

In addition, Sarwal said that about 20 percent of non-kidney transplant patients will eventually require a kidney transplant, which "makes early detection of kidney injury with NephroSant's [Qsant] urine test an important value add for any transplant patient."

NephroSant is also looking into developing a test to monitor the health of the kidney donor following the transplant. Sarwal's team previously published a JAMA Network study regarding a 20-year follow-up trial on living donors that found they were at slightly higher risk of developing problems with their remaining kidney, especially individuals who had a comorbidity.

"Monitoring those living donors, at least with a urine-based test once a year, makes complete sense," Sarwal said. "It's almost a societal responsibility we have back to this group, who altruistically donates a kidney."