Dimension Therapeutics Inc (NASDAQ:DMTX) reported at the end of last week that it will present data from its phase 1/2 clinical trial of DTX101 for the treatment of hemophilia B, at some point during January 2017. The company picked up a decent close to the week, likely attributable to investors getting in ahead of the data release, and it’s become one to watch as we close out 2016 and look to early 2017 as bringing a number of major catalysts to the fore.
Dimension is up to the tune of 26% post announcement, but for a company of this size (just shy of $200 million at last count), there’s plenty more potential for upside if the upcoming data points to efficacy and safety. With this in mind, and ahead of the numbers hitting press, here’s what we are looking for.
First, a quick look at the drug in question.
DTX101, as mentioned, is targeting a condition called hemophilia B. Some readers might already familiar with the condition, and others might be familiar but not realize it – it’s often referred to as factor IX (FIX) deficiency, or Christmas disease. As a reference note, this naming has nothing to do with the Holiday. It’s a nod to the first reported and documented case, a patient called Stephen Christmas, back in 1952.
Anyway, back to the discussion.
Patients with FIX have a deficiency of the factor IX protein, which comes about as the result of a mutation in a gene called, you guessed it, factor IX. This deficiency means that blood doesn’t clot, and this has obviously implications for the patient in question. Dimension’s solution, DTX101, is to deliver functional versions of the factor IX gene by way of a recombinant adeno-associated virus (AAV) of serotype 10 (AAVrh10) vector. To simplify this explanation, it basically packages the gene in a virus, and introduces the virus to the patient. The virus then delivers the functional gene to patients’ cells, and the gene starts coding for functional versions of its protein. This, theoretically, should boost the levels of functional factor IX in patients, and in turn, should cure the disease – or at least go a long way to improving its severity.
The trial is a double cohort trial, and both cohorts have been dosed to completion. It’s the data from these cohorts that will hit press come January. So what are we looking for when the numbers hit?
The trial is a dose ranging/finding trial, so the endpoints target a combination of safety and efficacy. Specifically, the two co-primaries are the incidence of treatment-related adverse events by dosing group, at 52 weeks, and the change from baseline in FIX activity level, at six weeks.
So, using the first of these endpoints, we want to see a low rate of AEs associated with the various doses (there are four under investigation, ranging uniformly from 1.6 x 10^12 GC/kg to 1.0 x 10^13 GC/kg). In other words, we are looking for some indication that the drug is safe.
Looking at the second of the co-primaries, we are looking to the data to show an increased level of FIX activity across the study period, ideally in line with dosing levels, assuming a relatively uniform (or non existent) AE profile across the studied doses. In other words, we want to see the drug translate to the genes creating functional factor IX, and we want to see higher doses resulting higher factor IX production. This latter point isn’t overly important, but it strengthens the hypothesis from a statistical perspective, so it would reduce a certain degree of risk heading into the latter stages of the development pathway.
The lead secondary endpoint is the number of bleeding episodes requiring recombinant FIX infusion. When a patient starts to bleed, one of the current leading SOC measures is to initiate an infusion of healthy proteins, to facilitate clotting. This endpoint is looking at the impact of the drug on the patient’s need for this infusion. If this need is reduced, and the number of bleeding episodes requiring recombinant FIX infusion reduces across the 52-week period that the patient is under investigation, it’s an efficacy signal.
Trial data should hit, as mentioned, in January 2017, so we’ll be watching the turn of the year closely.
Trial protocol can e found here.