BOSTON (TheStreet) -- Let's interrupt the non-stop (and frankly, repetitive) chatter about hepatitis C drug price wars and turn our attention again to Regulus Therapeutics (RGLS - Get Report) and its experimental, injectable microRNA therapy RG-101.

New trial data from a group of hepatitis C patients treated with a higher dose of RG-101 are expected in early February, according to Regulus. The company's stock price doubled last October when the first slug of RG-101 data were announced, so it's a good time to review what we know about the drug and attempt to determine what the updated results might reveal.

RG-101 uses small (micro) snippets of RNA to disrupt the replication of the hepatitis C virus and lead to its elimination from the liver. Regulus views RG-101 as a potentially new way to treat hepatitis C with a single or even a few simple and easily tolerated injections. It's a controversial idea because the best hepatitis C therapy today are already considered to be incredibly convenient. Gilead Sciences' (GILD - Get Report) Harvoni requires patients to take a single, daily pill for eight or 12 weeks. No injections are needed. Abbvie's  (ABBV - Get Report) Viekira Pak is just as effective but with a few more pills. [RA Capital portfolio manager Peter Kolchinsky owns Regulus and wrote about the bull thesis for RG-101 earlier this month]

The initial clinical trial being run by Regulus couldn't be simpler to understand: Enrolled hepatitis C patients are treated with a single injection of RG-101, then they're followed to determine their viral load reduction over time.

Last October, Regulus reported the first results from the study using a 2 mg/kg dose of RG-101 in 14 patients. The average viral load reduction was 4.1 log at 29 days. The magnitude of the viral load reduction seen with RG-101 was similar to the most effective direct-acting antiviral pills but it took longer to get there -- 29 days compared to seven days for Gilead's "nuc" Sovaldi, for example.


Dropping hepatitis C viral loads is a good start, but the disease is cured by eliminating the virus from a patient's body and not letting it return. Last October, Regulus said six of the 14 patients treated with RG-101 had no detectable hepatitis C virus after 29 days. In hepatitis C jargon, that's a "rapid virologic response" or RVR of 43%. That's not so great compared to proven drugs like the nucs, which yield RVR rates of 80% plus on their own, or even 100% when combined with other drugs.



A hepatitis C patient is deemed cured if the virus remains undetectable for 12 weeks following the final treatment. In October, Regulus said three of the six RG-101-treated patients with an RVR at one month also had no detectable virus at two months (57 days.)

Regulus is expected to include longer-term follow-up data on the patients treated with the 2 mg/kg dose of RG-101 as part of the early February update. Pay close attention to see how many of these 2 mg/kg RG-101 patients remain virus free with longer follow up, perhaps even long enough to be deemed cured. Just as important will be any patients who were undetectable at two months but then experienced a relapse where the virus starting growing again.

Regulus treated another 14 hepatitis C patients with a higher, 4 mg/kg dose of RG-101. The company will provide the initial results from these patients as part of the early February update, too. Will the higher dose lead to a greater average reduction in viral load? Will the average viral load reduction remain similar but the speed of the response accelerate? Will the higher dose lead to more patients achieving an undetectable viral load?

These are all the questions waiting for answers when Regulus updates the RG-101 study in early February.

Adam Feuerstein writes regularly for TheStreet. In keeping with company editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.