LONDON — An experimental blood cancer drug from MorphoSys hit its primary target in a pivotal trial, the company announced late Monday, but the drug faltered in addressing patient symptoms, causing the company’s stock to fall in early Tuesday trading.

In the Phase 3 trial, the German company was testing its drug candidate pelabresib combined with the drug Jakafi against a Jakafi-placebo duo in patients with newly diagnosed myelofibrosis, a type of rare blood cancer. Jakafi is a standard myelofibrosis treatment.

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The drug combination succeeded on its primary endpoint, with 66% of patients seeing at least a 35% reduction in spleen volume after 24 weeks versus 35% on the placebo regimen — an improvement the company in a release called “statistically significant and clinically meaningful.” Myelofibrosis is a rare bone marrow cancer that causes low blood cell counts and enlarged spleens, so reducing spleen volume is commonly used as the primary efficacy goal in clinical trials.

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