  Let $p$ be a prime number, $G$ be a finite $p$-group and $K$ be a field of
characteristic $p$. The Modular Isomorphism Problem (MIP) asks whether the
group algebra $KG$ determines the group $G$. Dealing with MIP, we investigated
a question whether the nilpotency class of a finite $p$-group is determined by
its modular group algebra over the field of $p$ elements. We give a positive
answer to this question provided one of the following conditions holds: (i)
$\exp G=p$; (ii) $\cl(G)=2$; (iii) $G'$ is cyclic; (iv) $G$ is a group of
maximal class and contains an abelian subgroup of index $p$.
