  We study new supergravity solutions related to large-$N_c$ ${\cal N}=1$
supersymmetric gauge field theories with a large number $N_f$ of massive
flavors. We use a recently proposed framework based on configurations with
$N_c$ color D5 branes and a distribution of $N_f$ flavor D5 branes, governed by
a function $N_f S(r)$. Although the system admits many solutions, under
plausible physical assumptions the relevant solution is uniquely determined for
each value of $x\equiv N_f/N_c$. In the IR region, the solution smoothly
approaches the deformed Maldacena-N\'u\~nez solution. In the UV region it
approaches a linear dilaton solution. For $x<2$ the gauge coupling $\beta_g $
function computed holographically is negative definite, in the UV approaching
the NSVZ $\beta $ function with anomalous dimension $\gamma_0= -1/2$
(approaching $-3/(32\pi^2)(2N_c-N_f)g^3$)), and with $\beta_g \to-\infty $ in
the IR. For $x=2$, $\beta_g$ has a UV fixed point at strong coupling,
suggesting the existence of an IR fixed point at a lower value of the coupling.
We argue that the solutions with $x>2$ describe a "Seiberg dual" picture where
$N_f-2N_c$ flips sign.
