There are clinical research trial that achieved remision in a large number of cats on Lantus.
And there is the experience of the members of this board who have achieved remission on Lantus, Levemir, ProZinc, PZI, ...
A great deal of it has to do with the availability of the person to do home blood glucose testing on a regular basis and a commitment to making a food change to low carbohydrate canned or raw food.
Sometimes, this means going against what your vet recommends and even pushing for something different.
We recommend testing with an inexpensive human glucometer and inexpensive test strips, not the expensive pet meters and expensive test strips, then using cat specific reference numbers. Your vet may not suggest testing, or may tell not to test, or may sell you a meter that costs over
$100 with test strips at over $1 each (2 tests a day is roughly $30/month.)
We recommend over the counter, low carbohydrate food like Friskies pates, not pricey vet prescription food which is no better nutritionally.