  We consider the inhomogeneous biharmonic nonlinear Schr\"odinger equation
(IBNLS) $$ i u_t +\Delta^2 u+\lambda|x|^{-b}|u|^\alpha u = 0, $$ where
$\lambda=\pm 1$ and $\alpha$, $b>0$. We show local and global well-posedness in
$H^s(\mathbb{R}^N)$ in the $H^s$-subcritical case, with $s=0,2$. Moreover, we
prove a stability result in $H^2(\mathbb{R}^N)$, in the mass-supercritical and
energy-subcritical case. The fundamental tools to prove these results are the
standard Strichartz estimates related to the linear problem.
