Prothena's PRX012 Shows Promising Reduction in Amyloid Plaque

By Ahmed Jameison • Thursday, August 28 10:27 • Permanent Link

Prothena Corporation plc (NASDAQ:PRTA) has released the results from the Phase 1 ASCENT clinical program for its potential once-monthly, subcutaneous anti-amyloid beta antibody, PRX012. The program demonstrated a dose* and time-dependent reduction in amyloid plaque, with a mean reduction in amyloid PET to 27.47 centiloids (CL) at the 400 mg dose level after 12 months. The FDA-approved anti-amyloid beta antibodies have defined amyloid negativity thresholds of ≤30 CL or ≤24.1 CL.

However, PRX012 was associated with higher overall ARIA-E (amyloid-related imaging abnormalities edema) rates relative to FDA-approved anti-amyloid beta antibodies, making it less appropriate for the patients studied in the ASCENT clinical program. When ARIA-E did occur, the characteristics were similar to those reported following treatment with other anti-amyloid beta antibodies.

The safety profile indicated that PRX012 was generally well-tolerated across all dose cohorts of the trial, with low injection site reactions (4.1%) and low treatment emergent anti-drug antibodies, which were generally transient with titer values close to the assay's detection threshold.

For the 200 mg dose level, participants received the dose in two separate cohorts (a core and an expansion cohort). The baseline mean CL values for the placebo, 45 mg, 70 mg, 200 mg, and 400 mg groups were 77.74, 75.64, 75.62, 75.47, and 70.95, respectively. After 6 months, the mean CL values were 77.84, 77.39, 67.44, 68.83, and 58.66, respectively. At 12 months, the mean CL values for the 200 mg group were 61.60, and for the 400 mg group, the value reduced significantly to 27.47.

Prothena plans to explore potential partnership interest to further develop PRX012 and its preclinical PRX012-TFR (transferrin receptor) antibody, which may represent an opportunity to significantly lower the risk of ARIA and quickly reduce amyloid plaque with a once-monthly subcutaneous administration.

As a result of these announcements, the company's shares have moved 2.52% on the market, and are now trading at a price of $8.56. If you want to know more, read the company's complete 8-K report here.

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