NEW YORK – After the recent publication of a validation study for its cardiovascular risk test, heart disease diagnostic startup Prolocor is preparing its assay for commercialization and regulatory approval in the coming months.
The results of the 800-patient multicenter study were published last month in the Journal of the American College of Cardiology and validated the use of the biomarker FcγRIIa (pFCG) to determine a patient's risk of experiencing a cardiovascular event, such as myocardial infarction or stroke.
According to Prolocor Cofounder and CEO Peter DiBattiste, the Philadelphia-based company, which was founded in 2020, aims to address the "major unmet medical need" to risk-stratify patients who have established atherosclerosis, a manifestation of atherosclerosis, or are at high risk of clinical atherosclerosis but haven't yet been diagnosed. While there are multiple pharmaceutical options for these patients to avoid a recurrent cardiovascular event, most of these drugs cause bleeding, and physicians may be reticent to use them intensively or for a long period of time.
DiBattiste's partner and cofounder David Schneider has been studying platelets for years and has focused on one protein receptor: FcyRIIa, which sits on a platelet's surface and "participates, in a very meaningful way, in the clotting process." Whenever a platelet is activated, the receptor clusters on the platelet surface and initiates a signaling cascade that amplifies the platelet activation. Schneider then started to collect data "looking at the association between this marker and risk for future events," DiBattiste said.
In a single-center study published in 2018 and conducted at the University of Vermont, Schneider collected blood samples from 200 patients who had experienced heart attacks, measured pFCG, and then followed those patients for two years after the heart attacks. He found a "striking association" between high expression of pFCG and the likelihood of an additional cardiovascular event, DiBattiste said. Patients with a high expression of the marker had a fourfold higher rate of having a heart attack or stroke or dying.
However, Prolocor knew one study wasn't enough and embarked on its recently published multicenter study to see if that data could be replicated, testing whole-blood samples from patients who presented in the hospital with a heart attack and following those patients for at least 18 months. To be eligible for the study, patients had to have at least two of five key characteristics: they must be older than 65, have multivessel coronary artery disease, have chronic kidney disease, have diabetes mellitus, or have had a previous myocardial infarction.
The firm's test is based on flow cytometry, which the company uses because of its "precision and accuracy," DiBattiste said. Prolocor's team discussed using a simpler methodology, such as ELISA, but "if we wanted to quantify the expression of the receptor, then we wanted to use a highly refined technique," he added. "The most important thing for us is to get the test right in the most accurate and precise way as possible."
The assay uses multiple antibodies to count the pFCG receptor because the protein is expressed on other cells, such as white blood cells and microparticles, so the company wanted to exclude other potential contaminating sources, he said. The assay includes one antibody that binds to an expression molecule specific to platelets, one that binds to the pFCG receptor, a third that binds to white blood cells, and a fourth that binds to microparticles.
The primary endpoint for the validation study was to get to 80 efficacy events, which it achieved six months ago and forms the basis of the JACC publication. The JACC study showed that myocardial infarction, stroke, and death occurred more frequently in patients with high expression of pFCG.
Patients with high pFCG likely should have extended treatment of a higher intensity, while a low expression indicates a patient should have treatment discontinued early, DiBattiste said.
The thresholds for high and low risk were based on earlier work performed by Schneider in other patient cohorts that observed the distribution of pFCG and found a natural cut point. DiBattiste noted that as the company collects more data, they will further refine the threshold for high and low risk patients. However, he added that the company wanted to use a dichotomous variable – high risk or low risk – because cardiologists had a "great desire" for a simple result indicating high or low risk rather than a numerical value.
Although Prolocor feels that it has established the utility of its assay to help assess the risk of cardiovascular events, DiBattiste emphasized that the firm is not proposing that its test should be the only tool used. "We don't propose this should be used in replacing clinical judgment" or other risk factors like age or renal function. "All of those things also contribute to the risk," he said, and Prolocor's test can be a "powerful addition that can really help with these millions of decisions."
In addition to the JACC study, the firm has another manuscript under review for publication that includes data it presented in an abstract in April at the American Association of Cardiology Scientific Sessions 2024. The data showed that the predictive value of the test is similar regardless of whether a patient is managed medically or with percutaneous coronary intervention, DiBattiste said.
It is also working on multiple other studies using grants from the National Institutes of Health, including an ongoing one for patients with intracranial atherosclerosis, an exploratory study in venous thromboembolism in cancer patients, and a study to determine the predictive value of the marker in venous clots.
The firm is also planning to conduct a study to validate its test for US Food and Drug Administration approval, as well as a clinical utility study to determine if ordering the test enables physicians to modify treatment plans and an outcomes study.
Prolocor is taking a "two-pronged commercialization approach," DiBattiste noted. It will first offer its test in a CLIA-certified laboratory and then develop in vitro diagnostic kits that it will take through the FDA. The firm has already had multiple pre-submission meetings with the FDA and expects to have a third in the next few months to discuss the company's plans for analytic validation, he said.
In the meantime, the company is seeking laboratory partners to conduct the test — although Prolocor has its own laboratory and originally planned to perform the test in-house, that laboratory is being used for research. Using an outside laboratory "will be a more expeditious way to launch the test commercially," according to DiBattiste. It is aiming to find a single laboratory that is a regional provider of flow cytometry tests because Prolocor would "prefer to work with a lab that can do this in their sleep," he said.
Prolocor is planning a pilot launch of the assay to start because it needs to prove that there is "a real demand for this test," that the company can operationalize the test, and that payors will pay for the test, he said. The firm thus far has received a positive response from clinicians and positive feedback in its payor research and is "pretty confident" in its test, he added.
For reimbursement, there is an existing pathway that Prolocor can use as a model for its test. Because flow cytometry tests already have CPT codes for detection of biomarkers and interpretation of a test, "if we use that as a scaffold we have a justification for the price," DiBattiste said.
The firm is also targeting a $15 million Series A financing round in 2025 that will help it perform additional clinical trials and get the test "up and running," he said. Thus far, the firm has received $6.2 million in NIH grants, $3.2 million in an initial seed round, and another $1.7 million in a seed extension round. Laboratory Corporation of America has invested twice in the seed round and the seed extension, he noted.
In DiBattiste's view, Prolocor's closest competitors for its test are clinical risk scores, such as the thrombolysis in myocardial infarction (TIMI) Risk Score that estimates mortality for patients with unstable angina and non-ST elevation myocardial infarction, and the GRACE acute coronary syndrome (ACS) Risk and Mortality Calculator that estimates admission and six-month mortality for patients with ACS. However, those risk scores are "cumbersome" and require the input of multiple clinical factors, such as creatine levels, age, heart rate, and blood pressure.
Fellow startup Prevencio has also launched a predictive test, but its assay predicts atherosclerosis more than subsequent thrombotic risk, he said. In addition, Prevencio's test uses multiple markers to come up with a score, in contrast to Prolocor's single-marker assay. Prevencio's HART CVE assay determines a patient's one-year risk of heart attack, stroke, or cardiac death using an artificial intelligence-based algorithm consisting of NT-proBNP, Kidney Injury Molecule-1, osteopontin, and TIMP-1.
The other risk scores and tests that are "tangentially related are not either as predictive or as easy to comprehend and incorporate into practice as I think our test will be," DiBattiste said.