MBX Biosciences Shares Drop 19.6% Despite 57% One-Year Responder Rate
MBX•MBX Biosciences shares fell 19.6% premarket after reporting one-year extension data for canvuparatide showing a 57% responder rate versus 63% at 12 weeks. The open-label study reported 90% retention, normalized serum calcium levels, reduced 24-hour urinary calcium excretion and sustained eGFR improvements with no new serious adverse events.
1. Share Price Reaction
MBX Biosciences shares dropped 19.6% in premarket trading following publication of the one-year extension data for canvuparatide, signaling investor concerns despite continued efficacy signals.
2. One-Year Efficacy Results
The open-label extension study showed that 57% of patients met the composite responder criteria after one year of once-weekly canvuparatide treatment. This rate was slightly below the 63% responder rate observed at the 12-week mark of the Phase 2 Avail study but still indicates sustained clinical benefit.
3. Patient Retention and Safety
Of participants entering the extension study, 90% remained on treatment through the one-year follow-up, underscoring strong retention. No treatment-related serious adverse events were reported, and most adverse events were mild or moderate, with injection-site reactions affecting about 10% of patients.
4. Biomarker Improvements
Mean serum calcium levels remained within normal range and average 24-hour urine calcium excretion declined from baseline. Researchers also observed eGFR improvements emerging by Week 12 and maintained through the one-year period, indicating enhanced kidney function.
