Latex can be butylized so it achieves a compromise between low weight, low rolling resistance and low leakage.
This was achieved by a French engineer, Mr. Boule and was marketed for some years under the AIR-B name.
I still have some in my cellar but they're way heavier than a nice Vred anyways.
Unfortunately, as with most things too good for their own good, the company was bought by Michelin in the same way they bought up other too bright ideas and was subsequently frozen.
Panaracer, a Japanese subsidiary of Pana (fill in the dots), has done its own research and came up with a butyl/latex mixture IIRC, that has similar properties as the AIR-B inner tube. Keep in mind, however, that rolling resistance was not the main target in these days as little research had been done in that particular area.
What they were after was a low weight latex inner tube that held air longer than mere latex and that was that.
Japanese based Panaracer has other proprietary mixtures of butyl and other chemicals though that are little known abroad and excellent tyres to boot.