  We analyze the renormalization group flow in a recently constructed class of
integrable sigma-models which interpolate between WZW current algebra models
and the non-Abelian T-duals of PCM for a simple group G. They are characterized
by the integer level k of the current algebra, a deformation parameter lambda
and they exhibit a remarkable invariance involving the inversion of lambda. We
compute the beta-function for lambda to leading order in 1/k. Based on
agreement with previous results for the exact beta-function of the non-Abelian
bosonized Thirring model and matching global symmetries, we state that our
integrable models are the resummed version (capturing all counterterms in
perturbation theory) of the non-Abelian bosonized Thirring model for a simple
group G. Finally, we present an analogous treatment in a simple example of a
closely related class of models interpolating between gauged WZW coset CFTs and
the non-Abelian T-duals of PCM for the coset G/H.
