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PsoriasisDx Says Gene Test for Early Detection of Psoriatic Arthritis Can Help Lessen Joint Damage

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By Turna Ray

PharmaGenoma subsidiary PsoriasisDx has launched a genetic test to help doctors identify patients at risk for developing psoriatic arthritis before they experience symptoms of the disease — the first genetic test of its kind, according to the firm.

Psoriatic arthritis is an irreversible disease of the joints that between 20 percent and 40 percent of psoriasis patients develop. Early detection of the disease before pain manifests can help lessen joint damage through early interventions, the company said.

John Koo, a professor of clinical dermatology at the University of California, San Francisco, and a member of the company's clinical advisory board, said in a statement that current treatments for PsA are "effective at controlling inflammation and arresting joint destruction, but are ineffective at reversing joint damage.”

As a result, early detection of the likelihood of PsA should help ensure that those patients who need those interventions receive them before the onset of inflammatory arthritis.

The PsoriasisDX Genetic Test costs $399. The cheek swab-based test detects through sequencing the presence of an immune response gene variant called MICA-A9, which is present in approximately 60 percent of patients with psoriatic arthritis.

MICA-A9 as a prognostic marker for psoriatic arthritis has been replicated in several published studies. If the patient tests positive for the MICA-A9 variant, it means he or she has about a 60 percent chance of developing PsA. Meanwhile, negative tests for the MICA-A9 variant confer upon patients a 70 percent chance of not developing PsA.

In the May 1999 issue of Arthritis & Rheumatism, Segundo Gonzalez and colleagues from the department of immunology at Spain's Hospital Central de Asturias reported a higher frequency of MICA-A9 in 65 Spanish PsA patients compared to 177 healthy controls. In this study, the researchers found that MICA-A9 was not in linkage disequilibrium with HLA-Cw*0602 — a gene variant strongly associated with psoriasis — suggesting that MICA-A9 is not associated with psoriasis, but just psoriatic arthritis.

Gonzalez et al. confirmed the association with MICA, rather than HLA-B/C genes, with psoriatic arthritis in a Jewish population in a study published in Human Immunology in 2001.

PsoriasisDX CEO Andy Goren told Pharmacogenomics Reporter this week that the company filed multiple patents on screening for PsA, including the MICA-A9 marker. Goren would not disclose whether the company is planning to submit the test to the US Food and Drug Administration for regulatory clearance.

Currently, testing is performed in PharmaGenoma's CLIA-certified laboratory. "We may license to other laboratories in the future," Goren said. Once the genetic analysis is complete, test results are reported to the patient's doctor.

The psoriatic arthritis diagnostic test is the second product for PsoriasisDx's parent company, PharmaGenoma. Based in Irvine, Calif., PharmaGenoma previously introduced HairDx last year, a genetic screening test for female and male pattern baldness. The FDA has designated the HairDx test a Class I, low-risk medical device.

Goren said the company was planning to conduct additional clinical analysis to further validate the relationship between the MICA-A9 varian and PsA, but did not elaborate.

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