  In the molecular picture the hidden-charm, pentaquark-like $P_c(4450)$
resonance is a $\bar{D}^* \Sigma_c$ bound state with quantum numbers
$I=\tfrac{1}{2}$ and $J^P = \tfrac{3}{2}^-$. If this happens to be the case, it
will be natural to expect the existence of $\bar{D}^* \bar{D}^* \Sigma_c$
three-body bound states. The most probable quantum numbers for a bound
$\bar{D}^* \bar{D}^* \Sigma_c$ trimer are the isoscalar $J^P = \tfrac{1}{2}^+$,
$\tfrac{5}{2}^+$ and the isovector $J^P = \tfrac{3}{2}^+$, $\tfrac{5}{2}^+$
configurations. Calculations within a contact-range theory indicate a trimer
binding energy $B_3 \sim 3-5\,{\rm MeV}$ and $14-16\,{\rm MeV}$ for the
isoscalar $\tfrac{1}{2}^+$ and $\tfrac{5}{2}^+$ states and $B_3 \sim 1-3\,{\rm
MeV}$ and $3-5\,{\rm MeV}$ for the isovector $\tfrac{3}{2}^+$ and
$\tfrac{5}{2}^+$ states, respectively, with $B_3$ relative to the $\bar{D}^*
P_c(4450)$ threshold. These predictions are affected by a series of error
sources that we discuss in detail.
