"IMPRIME-1’s main goals are overall response rate and safety — but researchers also will assess duration of responses, time to disease progression or death, and overall survival as secondary measures.
Participants received Imprime PGG as an intravenous (into-the-vein) injection on days 1, 8, and 15 of each 21-day cycle, while Keytruda was administered on day 1 of each cycle, also as an IV injection. Computed tomography (CT) scans were used to assess treatment response, and were taken at the study’s start and every six weeks thereafter until the cancer progressed.
At the time of the analysis, all 44 patients had been enrolled and receiving therapy for at least 12 weeks. After a median follow-up of 19.1 months, a total of 15.9% of patients (7 participants) had responded to the combination, with one complete response and six partial responses. An additional 40% had their disease stabilized — meaning tumors didn’t grow or shrink significantly — for longer than 12 weeks. Four participants had stable disease for 24 weeks or longer.
The median overall survival is 16.4 months, with 57.6% of patients living past the one-year mark.
A majority of patients (62.5%) had a reduction or stabilization of their target lesions. More than half of patients (53.7%) stopped the treatment due to new lesions or the increase of non-target lesions, even if the measured lesion was shrinking or stable. Patients with this mixed response pattern, however, showed increased overall survival.
Overall survival benefits were seen in three subgroups of patients: those with shrinkage of any measured lesion, whose risk of death was reduced by 67%; those with a more than 10% reduction in total tumor burden at 12 weeks, whose risk was reduced by 86%; and those whose total tumor burden dropped below baseline levels at any time — who saw a 56% reduction — regardless of the effects on new lesions and non-measured lesions."
