John Mascarenhas, MD, Icahn School of Medicine at Mount Sinai, New York City, New York, spoke about the latest in myelofibrosis (MF) treatment options in a presentation titled “Novel Combination and Non-JAK Inhibitor Therapies on the Horizon.”

This research was presented at the 2024 Annual Society of Hematologic Oncology (SOHO) meeting in Houston, Texas.

Transcript:

Hi, my name is John Mascarenhas. I am the director of the Center of Excellence for Blood Cancers and Myeloid Disorders here at Mount Sinai in New York City. I'm going to be reviewing what's on the horizon for myelofibrosis as we presented at the SOHO 2024 meeting

To level set, myelofibrosis right now has 4 approved JAK inhibitors, ruxolitinib, fedratinib, pacritinib, and momelotinib. And with those 4 drugs we're able to define niches, whether it's anemia or thrombocytopenia or second-line to address splenomegaly in patients with myelofibrosis.

What I would propose is on the horizon are non-JAK inhibitor therapies and combination therapies. The 2 trials that I want to highlight at highest level is the TRANSFORM-1 study, which was navitoclax, the oral BCL- 2/BCL-X inhibitor added to ruxolitinib, versus ruxolitinib plus placebo in patients who are JAK-inhibitor naive who have intermediate 2 or high-risk disease. In this study, we saw a doubling of the spleen volume response at 24 weeks, but no significant difference in symptom score. There were a lot of interesting correlates which suggest on-target activity, and there were some toxicity issues with myelosuppression overall. The trial will unlikely provide results that will move the drug forward, but was very informative indicating our ability to use [ ] drugs in combination with the JAK-inhibitor to get deeper responses.

The second trial that was concurrent to the TRANSFORM-1 study was the MANIFEST-2 study, which was a combination of pelabresib, the oral BET-inhibitor, with ruxolitinib versus ruxolitinib plus placebo in patients with JAK-inhibitor naive myelofibrosis who have intermediate-1 in higher-risk disease. These were patients who in some cases were earlier on in disease course. And in this study we also saw a doubling of spleen volume response at 24 weeks, much like the navitoclax study, but we saw a trend towards improvement in symptom score with a difference of about 2 points on the [total symptom score] (TSS), suggesting that we can improve upon the symptoms, beyond ruxolitinib alone, but capped by fatigue, which is very hard to improve upon.

We also saw further reductions in biomarkers like NF-κB-regulated gene sets, bone marrow fibrosis and deeper JAK2 V617F [ ] reduction, again, suggesting on-target disease modifying capabilities of this rational combination of pelabresib plus ruxolitinib. This study is ongoing. [We will] continue to follow up data beyond week 48 to see if there's durable responses. And ultimately, can we see improvements in progression-free survival, and with longer-term follow-up, is there a difference in overall survival when you combine these drugs in the upfront setting?

I think the other aspect of myelofibrosis where we see progress is the concept of add-on strategies. I think the trial to highlight from that perspective is an ongoing study, which is the addition of navtemadlin, the oral MDM-2 inhibitor, which has significant activity in wild-type P53 chronic phase myelofibrosis to ruxolitinib in patients who have a suboptimal response to single agent ruxolitinib. So rather than upfront, an add-on salvage strategy with this drug. We already have really, um, compelling phase 1b data demonstrating both clinical activity and significant biomarker activity suggestive of disease modification with navtemadlin.

The ongoing upfront study that's still accruing is the selinexor plus ruxolitinib versus ruxolitinib plus placebo in JAK-inhibitor naive patients. Very similar designed to the MANIFEST-2 and the TRANSFORM-1 study. Selinexor is an approved drug in B-cell malignancies and plasma cell dyscrasias as an XPO-1 inhibitor and has significant rationale also targeting the P53 pathway with, very compelling preclinical and early clinical data suggesting significant activity. We look forward to seeing how these approaches, whether it's upfront approaches with various rational drugs or salvage approaches, ultimately pan out and try to move the treatment paradigm to combination therapies.

In a non-combination setting, 2 drugs I'm going to highlight for the audience are the telomerase inhibitor imetelstat, which is a drug now approved for transfusion-dependent lower risk myelodysplastic syndromes (MDS). In this setting, [in] myelofibrosis, it's for patients who failed ruxolitinib with expected poor survival. This is a randomized study to imetelstat versus best available therapy, excluding JAK inhibitors. This is a large global study that's more than halfway accrued with a primary end point of overall survival. This is the only study in MF that I'm aware of where survival is the end point. This becomes a really important study to determine whether we can look at end points beyond spleen and symptom, with drugs that have the potential to modify the, the malignant stem cell pool that drives the disease.

Lastly, TP-3654, which is a Sumitomo selective oral investigational PIM-1 kinase inhibitor, has also presented very elegant data demonstrating lack of myelosuppression that's associated with pan-PIM-kinase inhibitors, while attaining spleen and significant symptom response. Also correlating downregulation of inflammatory cytokines with clinical responses. That's a drug that's going to move into combination phase studies and will join the pack on this theme.

In summary, a lot of movement in, in myelofibrosis with a lot of combination therapies, a lot of novel therapies, even salvage therapies and even a trial now with overall survival. It's an exciting time and we look forward to seeing some of these results mature. Thanks very much.

Source:

Mascarenhas J. Novel Combination and Non-JAK Inhibitor Therapies on the Horizon. Presented at the 2024 Society of Hematologic Oncology meeting. Houston, Texas; September 4-7, 2024.