The recently discovered $P_c(4380)^+$ and $P_c(4450)^+$ states at LHCb have masses close to the $bar DSigma_c^*$ and $bar D^*Sigma_c$ thresholds, respectively, which suggest that they may have significant meson-baryon molecular components. We analyze these states in the framework of a constituent quark model which has been applied to a wide range of hadronic observables, being the model parameters, therefore, completely constrained. The $P_c(4380)^+$ and $P_c(4450)^+$ are studied as molecular states composed by charmed baryons and open charm mesons. Several bound states with the proper binding energy are found in the $bar DSigma_c^*$ and $bar D^*Sigma_c$ channels. We discuss the possible assignments of these states from their decay widths. Moreover, two more states are predicted, associated with the $bar DSigma_c$ and $bar D^* Sigma_c^*$ thresholds.
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