GeneSight trial miss leaves Myriad depressed
In missing its primary endpoint in a crucial clinical trial, Myriad Genetics’ test for patient response to major depressive disorder treatments, GeneSight, leaves the company without much hope of achieving the increased reimbursement rate and therefore the increased sales it had sought.
The product is a vital one for Myriad since sales of its tests for hereditary diseases, including cancer, are falling fast. GeneSight accounted for more than 10% of Myriad’s overall sales last year and success in this study could have boosted this markedly; the failure wiped 16% off Myriad’s share price yesterday.
GeneSight analyses 12 different genes, including those for serotonin receptors and the cytochrome p450 enzymes which are instrumental in drug metabolism, with the aim of detecting any mutations and determining their likely influence on a patient’s response to more than 55 psychotropic drugs. It is intended for use in patients who have already been treated with two or three antidepressants with no effect.
The trial in question was not aimed at gaining approval for GeneSight. Though the test is not approved by the FDA, it is on sale in the US under the Clia waiver programme, as a so-called lab-developed or home-brew test.
Instead Myriad was conducting the study in order to gain a higher rate of reimbursement in the US. Commercial reimbursement for GeneSight sits at around $120 per test, according to Leerink analysts, but Myriad was targeting a rate of around $2,000 per test.
The trial enrolled 1,200 patients with major depressive disorder. All the patients were tested with GeneSight, but they were then divided into two groups: in one, the GeneSight results was used to guide drug treatment, and in the other the patients were treated without reference to the GeneSight data – in other words, as their doctors saw fit.
The primary endpoint, per clinicaltrials.gov, was change from baseline on the 17-item Hamilton depression (HAMD-17) score after eight weeks of treatment. It was missed, with Myriad saying that though patients receiving GeneSight-guided therapy had a greater reduction in HAMD-17 scores after eight weeks compared with the treatment-as-usual group, the difference did not reach statistical significance with a p value of 0.1.
The good news is that the trial met a couple of secondaries: remission, as defined by a HAMD-17 score of 7 or less, and response, defined as a HAMD-17 reduction of more than 50%. Patients receiving GeneSight-guided therapy achieved clinically meaningful and statistically significant improvements on these measures.
Myriad bought GeneSight’s originator, Assurex, for $225m last year. The test brought in revenues of $78.3m in fiscal 2016.
Analysts from Leerink believe that the data on remission and response might be enough to drive increased use of the test by psychiatrists. But they are unlikely to lead to the test’s inclusion in clinical guidelines or, therefore, boost higher reimbursement of GeneSight.
For that, Myriad would have to demonstrate the test’s absolute clinical necessity – that it can put patients on the right drugs straightaway, thus saving the healthcare system the cost of supplying ineffective drugs. At this point that looks unlikely. GeneSight is currently forecast to have sales in 2022 of $183m, according to EvaluateMedTech’s sellside consensus. If this is revised upwards, it will not be by much.