Algorithms for finding clique in bounded-degree graph
Eppstein, Löffler, and Strash modified the Bron-Kerbosch algorithm, obtaining an algorithm that lists all maximal cliques in $O(dn 3^{d/3})$ time, where $d$ is the degeneracy of the graph (note $d \le \Delta$).

The same idea can be extended for the maximum clique problem in $d$-degenerate graphs, and the runtime can be improved to $O^*(2^{d/4})$.