Remix Therapeutics, a clinical-stage biotechnology company headquartered in Watertown, Massachusetts, announced that the US FDA has granted Fast Track designation to REM-422, an oral small molecule MYB mRNA degrader, for the treatment of recurrent, metastatic, or unresectable adenoid cystic carcinoma in patients whose tumors express MYB transcripts containing a poison exon. Remix Therapeutics REM-422 is the first compound in its class to reach this regulatory milestone in ACC.
The Fast Track designation enables more frequent FDA interactions and eligibility for rolling review. REM-422 had previously received Orphan Drug Designation for both ACC and acute myeloid leukemia (AML).
REM-422 functions by inducing incorporation of a poison exon into the MYB mRNA transcript, triggering nonsense-mediated decay and suppressing MYB protein expression. MYB dysregulation is a hallmark oncogenic driver in ACC, a rare malignancy arising most commonly in the salivary glands. The designation was based on preliminary Phase I results from the ongoing ARIA (A study of REM-422 In Adenoid cystic carcinoma) trial, a Phase I/II, open-label, multicenter study (NCT06118086) evaluating safety, pharmacokinetics, and anti-tumor activity. The company reported that REM-422 demonstrated proof-of-mechanism and proof-of-concept in ACC along with a tolerable safety profile, though specific response rates, p-values, and detailed adverse event data were not disclosed. A separate Phase I study has also evaluated REM-422 in patients with recurrent or metastatic ACC. In parallel, REM-422 is being investigated in AML and high-risk myelodysplastic syndrome (HR-MDS), though no expedited designations have been announced for those indications beyond Orphan Drug status.
Research context
Adenoid cystic carcinoma treatment remains an area with no approved systemic therapies. ACC is characterized by perineural invasion, late recurrence, and a propensity for distant metastasis, requiring prolonged follow-up. Chemotherapy, kinase inhibitors, and immunotherapy have each been studied in ACC with limited efficacy. The absence of approved options for recurrent, metastatic, or unresectable disease has left clinicians reliant on surgery and radiation where feasible, with no standard-of-care systemic regimen.
The competitive landscape for ACC is sparse. KB-0742, an oral CDK9 inhibitor developed by Kronos Bio (now part of Rigel Pharmaceuticals), has shown preclinical activity in transcription factor fusion-driven ACC patient-derived models, representing an alternative strategy of targeting transcriptional dependencies. However, KB-0742 acts on CDK9, a general transcriptional regulator, rather than directly degrading MYB mRNA. REM-422 differs mechanistically by exploiting RNA processing biology to eliminate the MYB transcript itself through poison exon inclusion and nonsense-mediated decay. This distinction positions REM-422 as the only clinical-stage agent designed to directly reduce MYB protein levels via mRNA degradation, rather than inhibiting downstream kinase activity or broader transcriptional machinery.
The FDA Fast Track designation in oncology for REM-422 reflects the regulatory pathway's applicability to rare solid tumors where no approved therapies exist. Whether the Phase I results from the ARIA trial translate into durable responses in a larger cohort remains to be established as the study progresses into dose expansion. Mature efficacy and safety data, including overall response rate and duration of response, have not yet been reported publicly.
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