ABL Bio said Tuesday that it has submitted a protocol amendment to the U.S. FDA for its phase 1 clinical trial of ABL301 at higher doses.

If the amended protocol wins the FDA’s approval, the company plans to conduct a single-ascending dose study and a multiple-ascending dose study at higher doses of ABL301 above 20 mg/kg.

"The phase 1 single-ascending dose and multiple-ascending dose studies will evaluate the safety and tolerability of single and repeated doses of ABL301 in healthy adults," ABL Bio said.

The protocol change request follows the initiation of ABL301 in the U.S. phase 1, where the FDA expressed concerns about the high dose administered during the phase 1 protocol and requested high-dose GLP (good laboratory practice) toxicity nonclinical studies and additional data submissions, which the company said reaffirmed safety in September.

ABL301 is a bispecific antibody candidate being developed by ABL Bio for treating neurodegenerative diseases, including Parkinson's disease. It utilizes a blood-brain barrier (BBB) shuttle platform, Grabody-B, to effectively deliver antibodies that inhibit alpha-synuclein accumulation, the cause of Parkinson's disease, into the brain to improve therapeutic effectiveness.

In January 2022, ABL Bio entered into a collaboration and technology transfer agreement with Sanofi for up to $1.06 billion (about 1.38 trillion won), transferring global exclusive rights to develop and commercialize ABL301. Under the agreement, the ongoing phase 1 study of ABL301 will be led by ABL Bio, with Sanofi leading the phase 2 study.