The Wnt/β-catenin signaling pathway is known to play critical roles in a wide range of cellular processes: cell proliferation, differentiation, migration and embryonic development. Importantly, dysregulation of this pathway is tightly associated with pathogenesis in most human cancers. Therefore, the Wnt/β-catenin pathway has emerged as a promising target in anticancer drug screening programs. In the present study, we have isolated three previously unreported metabolites from an undescribed sponge, a species of Monanchora (Order Poecilosclerida, Family Crambidae), closely related to the northeastern Pacific species Monanchora pulchra, collected from deep waters off the Aleutian Islands of Alaska. Through an assortment of NMR, MS, ECD, computational chemical shifts calculation, and DP4, chemical structures of these metabolites have been characterized as spirocyclic ring-containing sesterterpenoid (1) and cholestane-type steroidal analogues (2 and 3). These compounds exhibited the inhibition of β-catenin response transcription (CRT) through the promotion of β-catenin degradation, which was in part implicated in the antiproliferative activity against two CRT-positive colon cancer cell lines.