How difficult is it to make a shRNA/miRNA/siRNA to silence/knockdown NaV1.7 voltage gated sodium channels in humans?
The major hurdle for novel treatments to make it into humans is the assessment of its merits and added value over existing, proven treatments. And more importantly, the safety for humans has to be validated to a sufficient extent. The notorious from bench to bedside (Goldblatt &amp; Lee, 2010) bottle neck. To answer your questions:


Technically, going from animals to humans may be a small step. Just increase the dose according to body weight. However, ethically it is a giant step. In fundamental research, lab animals are typically investigated only for the positive effects (e.g., amelioration of symptoms). In preclinical research, the animals have to be tested on side effects. Systemic injections, and even localized administration of potentially harmful virus vectors carries considerable risk. What if it returns to an infectious state? What are the side effects? Further, while animals can be treated systemically via iv injections, humans don't like needles. The FDA will put every possible danger and every possible discomfort to the patient into the spotlight.
Getting grants is hard. Going from bench to bedside is even harder, as the FDA, institutional review boards and the scientific community at large will scrutinize the plans.
To undertake clinical trials with humans is a team effort involving medical professionals, review boards, patients or healthy volunteers, an independent monitoring committee and so forth. It's not something you'll be doing in a few months. It can take years or decades to bring novel treatments to patients. It doesn't take one grant - it takes many, and development costs easily run into the tens of millions.


Reference
- Goldblatt &amp; Lee, Am J Transl Res (2010); 2(1): 1–18