Whiel I agree re practice, I actually think it's FAR more important to be 100% clear on your message. If you are confident in what you are saying, the rest matters less. And if you are trying to do an elevator pitch, the WHAT you say is absolutely the most important thing.
Start with the "so what"? WHY is this important? What will it solve? Who will benefit? Why should the people listening want to know more about YOUR subject? What's the benefit to them? Make sure you know that very clear.y.
Then think about what you can say tha tmakes that clear. this is not the time for wishy washy, humble statements that require inference and intuition from the audience. TELL them. "My research show sthat in 100 years, everyone will be dead". You don't need to prove it. This is 2 minutes to get them interested.
Play with the language. what is the strongest language you can use that will actually be true and tat you feel you could stand behind if one of these people want to discuss it with you later? Then look at it again and see if you can make it 5% punchier.
Once you've done all THAT work, trust me, your two minutes (which is literally 300 odd words so NOTHING), then suddenly you're half way there. THEN you practice.
(I train people on stuff like this and am actually working on a training program aimed specifically at people in your sort of situation so Iv'e given this a lot of thought).