A single injection of a microRNA therapeutic directed at a genetic target in the liver of hepatitis C patients produced a significant drop in viral load, according to interim results from an early-stage study announced Wednesday by Regulus Therapeutics(RGLS) - Get Report , the developer of the therapy, known as RG-101. 

Regulus shares are up 119% to $14.84 on the RG-101 results. Hepatitis C is an insanely crowded and competitive field, but investors see in the early Regulus RG-101 data the potential for a new way to cure the liver disease with a single or even a few simple and easily tolerate, under-the-skin injections, instead of four, eight or 12 weeks of daily pills. 

But you're getting way ahead of the facts if you think Regulus has a game-changing hepatitis C therapy in its grasp already. There's a lot more work to be done and questions to be answered. 

Here's what we know right now: In 14 patients with hepatitis C, a single injection of RG-101 yielded an average viral load reduction of 4.1 log at 29 days. The most potent hepatitis C "nuc" pills like Gilead Sciences'(GILD) - Get Report Sovaldi and the nuc Merck(MRK) - Get Reportacquired in the Idenix Pharma takeout both yield similar 4 log drops in viral load, but after only a week of dosing. Regulus' RG-101 is in the same potency neighborhood, which partially explains today's buzz. 

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. By this measure, RG-101 still needs to prove itself. 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. 

Regulus said three of the six RG-101-treated patients with an RVR at one month also had no detectable virus at two months. This suggests RG-101 might have some real potency but we need to see more and longer-term data to confirm. Regulus intends to continue to follow these patients in the study and provide updated results. A higher dose of RG-101 is also being studied, as is a regimen combining RG-101 injection with existing direct-acting oral hepatitis C pills. 

Based on the interim results from this small sample of hepatitis C patients, it's difficult to have confidence in the "home run" scenario by which a single or even a few injections of RG-101 on its own leads to the 95% plus hepatitis C cure rates which are now the standard set by Gilead with the just launched Harvoni and other regimens to be approved imminently. If RG-101 requires combination therapy with existing pills, the convenience factor disappears, so where would the injectable drug fit? With so much competition and cure rates nearing 100% already, it might be tough for Regulus to find a niche for RG-101. 

I'm not trying to rain completely on today's big move in Regulus' stock price, but it's important to understand the competitive context in hepatitis C. Even with today's doubling in stock price, Regulus' market cap is still below $700 million. Compare that to the $1 billion market cap of Achillion Pharmaceuticals(ACHN) - Get Report , which is developing a hepatitis C nuc also in early stages of testing but has yet to prove it can also hit the 4 log viral load reduction bogey. [We should know soon, as I explain in the blog post below.]

Regulus deserves a seat at the hepatitis C table with today's impressive but early data on RG-101. Let's see more. 

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.