Here's What Protalex Inc. Just Told Us With Its Latest Release

Protalex Inc. PRTX just announced that it has dosed the first patient in the third cohort of dose-escalating study in patients with persistent/chronic Immune Thrombocytopenia (ITP). This is the company's lead development program and the latest announcement marks both the clearing of a hurdle associated with the previous cohort and a march towards mid stage advance.

Here is a look at what just happened and what it means for shareholders and the company itself.

First, ITP is an autoimmune condition that's characterized by bruising and increased bleeding. Put simply, the immune system destroys existing platelets and inhibits the production of new platelets in the blood. Platelets are the cells that circulate in our blood system and help blood clot. Analysts peg the market size for this indication at around $928 million right now, and expect it to grow to just shy of $1 billion over the next ten years. It's not a particularly fast growing market, but the lack of effective treatment options in it right now means it's still a substantial opportunity for any company that can get an effective drug on shelves.

So, PRTX-100 works by binding to B-lymphocytes. B-lymphocytes are responsible for the destruction and removal of various cells, including platelets, so by binding to them, the drug can theoretically reduce the destruction of platelets in patients with ITP and – by proxy – help said patients maintain standard platelet counts.

The trial is a phase 1b study designed to investigate both safety and efficacy of PRTX-100. This is Protalex's lead candidate. A dose escalation study, meaning one with a number of cohorts across varying doses, is simple in its goals. The trial here has a maximum cohort number of five, meaning five groups getting different doses, spread across up to 30 patients. Each cohort will involve between three and six of these 30 patients and will receive a particular dose of PRTX-100, with this dose escalating in parallel with the cohorts' numerical escalation.

Patients receive four weekly intravenous doses of PRTX-100 and will be monitored for up to 48 weeks thereafter. The output from the monitoring will inform against a primary endpoint of safety and efficacy, immunogenicity, and pharmacokinetics spread across a variety of secondary endpoints

To illustrate how this works in practice, the first cohort received 3.0 µg per kilogram of PRTX-100. Once cleared for safety, the company then advanced the trial into cohort two and dosed another handful of patients with 6 µg per kilogram. A planned interim of this cohort just completed and greenlighted the advancing to cohort three, as part of which patients will receive 12 µg per kilo. If a feature interim analysis proves that this dose can be safe, the company will move into cohorts four and five, as part of which patients will receive 18 µg per kilogram and 24 µg per kilogram of PRTX-100 respectively.

When a company runs a dose escalation trial like this, we want to see safety first, followed by some early indication of efficacy and, ideally, efficacy in line with dosing levels. That is, the higher the dose, the higher the impact. We haven't seen enough data yet to say with any certainty whether dose correlated efficacy is evident, but management reported earlier this year (February) that early-stage efficacy was apparent and the advancing from one cohort to another suggests that safety is – as yet – no issue.

There's an early cohort abstract available here for anyone that wants to see the interim numbers.

Bottom line, then, is that the drug seems to be safe and we haven't had any indication that it's not working as expected.  It's worth noting that this is a European trial and it is running in parallel to a US-based trial, with the two called PRTX-100-203 and PRTX-100-202 respectively.

Protocols for both are available here:

US study

European study

Disclosure: The author has no positions in any of the stocks mentioned in this piece.