ASCO 2026 | Initial results from a Phase Ib/II trial of purinostat mesylate plus POM and DEX in R/R myeloma

Actually, this is the Phase I and IIA clinical trial for the combination with our compound. Our compound was called purinostat mesylate. We call that PM in short words, it’s easy to be recognized. Combined with pomalidomide and dexamethasone, which is, we call that a triple combination for the treatment of refractory and relapsed multiple myeloma treatment. Yeah, that is quite an interesting triple target. Actually, this study is open-label, parallel, controlled, and multicenter. So this clinical trial is recognized and led by two Chinese top myeloma centers. One is the Western China Hospital of Sichuan University. Another one is the Peking University People’s Hospital. So the co-PIs are Professor Liu Ting and another is Professor Liu Jing. 

So in terms of the dosing, we choose actually PM is a high HDAC inhibitor focused on the HDAC1 and HDAC2B. So this is a very high selectivity HDAC inhibitor in combo with another immunomodulatory agent treatment. So the dosing is totally different with another clinical trial. So actually we choose two cohorts, cohort 1 and cohort B. Cohort 1 doses are a little different than cohort B because we want to explore the quite dosage further for the phase three. So cohort A was fixed like that. So first of all, cohort A used a two-week on, and a one-week holiday, so schedule, in 21 days as a cycle. And this dosage is the same as our Phase I and IIA in China for the treatment for the hematological tumors. And cohort B uses a more split-out schedule. In this case, PM is given on day 1, 4, 8, and 15, in a 28-day cycle. So you can see there is a difference, because in cohort B, PM, as a quite strong high selectivity HDAC inhibitor, can have some side effects such as simple cytopenia and neutropenia. So cohort B gets the patient to have a more day holiday off so can avoid some toxicity for the hematological toxicity. So that is the difference between cohort A and cohort B. And in this case, the PM will be escalated from the low-dose to high-dose. So because we want to get the quite good doses for our combination with the pomalidomide and the dexamethasone like that. So actually we got the right doses which we expected. 

So what do we find out? So cohort A as we predicted, can get very good response for the OR, objective response rate, is over 50%. But, and we still observed the high, you know, high adverse, especially simple cytopenia and the neutropenia. So, but for cohort B, it’s quite good. We got a very good balance between the efficacy and the toxicity. For example, we still get a very high ORR with 43.75%. But the simple cytopenia, grade 3 simple cytopenia is not so high. It’s only 50%. So that is why we get the quite good balance between the response and the safety issue. So that is this triple target. That is why this triple combination for the treatment of RRMM, can get a good result. 

At the moment, in China, this triple combination is still going on. And after we got quite good cohort B, the right doses, we quickly go for the expansion for the 8.4 milligrams per square meters as the recommended doses for combination, for expansion. So after that, we total enrollment almost 26 patients for the PM treatment with pomalidomide and low-dose dexamethasone. So we totally got the 26 patients and they get a quite good response for the OR and the CR. So that is our result.

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