Absolutely! We sold 6-month subscriptions upfront to quite a few big brands before we had any type of beta in market (including category leaders Virgin and Open Colleges).
There were two key factors for us:
1. Trust (and this is the most important!)
The foundation for any customer relationship is trust (eg what makes them trust that you are capable of delivering, what makes them trust that you have the vision to drive incremental value for their business?) Is it your team's experience, is it the fact that you know someone they know, is it the fact that you are already delivering a great product and can show traction? Is it the fact that their smaller competitors are already your clients? Is it the fact that you have been covered in press and are seen as an expert? (Whatever it is that is going to drive trust in your pitch, use it!) We have found a lot of value in breaking down all our approaches to brands via our calls, emails and presentations into how each sentence is working to drive trust - if you aren't creating trust in the first sentence of your call and emails or the first slide of your presentation you are already starting at a disadvantage. Trust is what makes them buy from you.
2. Increase the reward and lower the risk
Big brands are risk averse - even the innovation teams don't want to be seen internally as a group of people who just throw money at new tech without any ROI. They too are responsible for meeting objectives and growing the value of their company.
We have found it very helpful to actually have a slide addressing these two factors transparently - there is no point dodging the issues that you know are going through their head and sweeping them under the rug so talk about them in the open. Put points in your presentation anticipating the challenges they may have around the risks of your business and how you are addressing them to lower their risk. It will show them that you appreciate their POV and are smart enough to have addressed them already.
Then put points down about how you are rewarding them for coming on board as early partners. Early bird discount, capped price extensions, promote them in your PR, provide them additional insights, give them direct access to your development feedback cycle etc.
As other people have mentioned, having enterprise case studies to refer to makes your job a hell of a lot easier. So address the risk and reward factors and the more you sign on the less these factors even matter.
Obviously this assume you have first done your research around your target market and exactly which key contact/department within the client is most likely to champion your product internally. Hope that helped.