** Shares of biotech firm Monopar Therapeutics MNPR.O rise 5% to $99 premarket

** Co says FDA granted rare pediatric disease designation to its experimental drug ALXN1840 for Wilson disease, a rare inherited disorder that causes toxic copper buildup in the body

** Monopar says the designation could qualify the company for a priority review voucher if the drug is approved

** Says such vouchers can be used to speed review of another medicine or be sold to other drugmakers

** Co's ALXN1840, a once-daily oral tablet, removed copper more effectively than current treatments in a late-stage study over 48 weeks

** Adds that the treatment showed a favorable safety profile in the study

** As of last close, stock up ~45% YTD