In a preliminary analysis of a phase 1 trial, CXCR4-enriched T regulatory cell therapy (CK0804) as an addition to ruxolitinib treatment demonstrated initial safety and promising clinical activity for patients with myelofibrosis receiving ruxolitinib who have palpable splenomegaly, symptoms, or grade 2 cytopenia.

These results were presented by Lucia Masarova, MD, The University of Texas MD Anderson Cancer Center, Houston, Texas, at the 66^th ASH Annual Meeting in San Diego, California.

Investigators explored this option due to research that suggested deregulated inflammatory pathways might contribute to suboptimal therapeutic efficacy of ruxolitinib for patients with myelofibrosis. In preclinical studies, cord blood-derived, CXCR4-enriched T regulatory cells showed ability to suppress inflammatory cytokines.

“This preliminary analysis of run-in phase of study evaluating CXCR4-enriched T [regulatory] cell therapy as addition to ruxolitinib shows initial safety with no myelosuppressive adverse events and promising clinical activity,” concluded Masarova and colleagues.

Transcript:

Hello, I'm Lucia Masarova, from MD Anderson Cancer Center in Houston, Texas. It's my pleasure to present results of our phase I, unique study, using Tregs [regulatory T-cell] therapy as an add-on to ruxolitinib here in ASH 2024 in San Diego.

So, this is our study that is running at MD Anderson Cancer Center, currently also enrolling at 2 other institutions, over at albert Einstein College of Medicine, as well as UC Davis. However, here we are presenting the results of a phase I, safety run-in cohort.

So why Tregs in myelofibrosis? That's a quite innovative approach which has not been tried before. And just briefly little bit into it, Tregs are FoxP3 CD4-CD 25+ and CD127low T-cells. They have various mechanisms how to rebalance immune suppression, as well as immune dysregulation that is so typical for patients with myelofibrosis, and very likely a reason of suboptimal responses. 

These cells are actually able to suppress the information as well as restore the equilibrium. So, there has been a first study published this year in New England Journal of Medicine Evidence on the first product called CK0801, which were HLA-matched Tregs cord blood-derived that were given to patients with acquired bone marrow failure syndromes, and also included for patients with myelofibrosis, with excellent safety and very interesting preliminary efficacy. 

So therefore, the next generation product that that is called CK0804 or CXCR4-enriched Tregs, has already shown preclinical models that were presented last year by oral presentation at ASH, that these cells have a better homing to bone marrow, so they go faster to their areas of information and they also have superior activity to suppress cytokines including TGF [transforming growth factor] beta, interferon or TNFs [tumor necrosis factors], compared to unmanipulated Tregs. 

This product has been taken into clinical testing and it's currently being an add-on therapy to myelofibrosis. So, we have an open study that is currently running in the expansion cohort, but the results here presented are safety running, 9 patients’ dose as an add on to ruxolitinib. So, patients eligible had to be on ruxolitinib for at least 3 months with stable dose of 2 months, I can tell you all of these patients were on RUX for at least 6 months or more, so all of them had sub optimal response, that means detectable spleen over 450CC's or by palpation, symptoms score more than 10 MPNs, or development of new cytopenias. Then they had edited Tregs given in an outpatient setting every month, intravenously over 10 minutes as a standard fixed dose of 100 million cells per dose.

The primary objective early study was safety, so we also were capturing, of course, early efficacy and a couple exploratory exciting end points, including cytokine analysis and immune reconstitution given the hypothesis of rebalancing the immune system.

So, among these 9 patients, the median age was 68 years, patients were on JAK inhibitors of a dose 10 mg twice a day or higher. None of these patients had the dose changed, including 6 months period post the last infusion. These infusions are given 6 times monthly and 7 out of 9 patients finished the whole planned 6 infusions. One patient has dropped from the study after cycle 2, the patient developed infusion reaction due to the self-preservant, called MSO, and then withdrew consent. One patient unfortunately died prior to the last infusion after 5 cycles or 5 infusions of the Tregs. Total of 49 Tregs were given to these patients and then we only had this one infusion reaction, otherwise there were no other cells related hematologic or non-hematologic toxicity, quite striking and exciting. There were only 2 non-related, non-hematologic adverse events that included infections.

Again, as I said none of these patients had changed to ruxolitinib, median time on ruxolitinib prior to enrollment was 3 years, including a patient that took ruxolitinib for more than 10 years before being enrolled in the study. This patient had quite significant symptoms, actually every single patient that was enrolled was symptomatic with median TSS score at the start of 26 and 6 of them had significant splenomegaly with symptoms that are derived from the spleen graph. We have had also 3 patients with significant anemia dependency and 6 out of 9 patients had anemia with hemoglobin below 8. 

In the molecular level, we had all kind of drivers, so they were patients with JAK2, [indiscernible], and every single patient had additional mutations with the most frequent being ASXL1 and TET2, so quite extensive populations. Safety was very concerning, but came excellent, actually no safety concerns, very quick ambulatory outpatient setting  these are core-derived T-cells, they are from umbilical cord, cryopreserved so frozen product, on demand, off the shelf, quickly delivered, no waiting, very great manufacturing getting these cells from the cord blood because these remain a naïve, hardwired Tregs with no memory cells, they have no plasticity and very low immunogenicity, so very reliable, very consistent manufacturing and again on demand outpatient setting.

So that was quite encouraging, and our patients actually loved to come for the cells because they felt immediately good. So that is one point where we have noticed every patient had improvements in the symptoms, we were using MPN-TSS SAF which is standard assessments for patient symptoms for myelofibrosis, and except for the decline of the symptoms, we have had officially 6 out of 9 TTS50 responders, which was reflected in improvements in the mean TSS score from the start until the end. Actually, the best drop was cycle 3 day 1, but it was persistent at the cycle 6 and even out of the follow up and was still statistically significant. 

Alongside this, we have noticed improvements in fatigue. Fatigue has also had significant drop from before the infusions and compared to the last infusion, and fatigue is a symptom that is hard to beat, so we were really excited to see this. Actually, fatigue reached the best significance 6 months after the last infusion. This effect was lasting and it's still ongoing in quite a lot of our patients. 

We also have noticed improvements in early satiety. Early satiety is a symptom that is related to splenomegaly, so 6 of these patients had significantly growing splenomegaly. We have noticed 1 that had what we call SVR35, which is 35% decline by imaging, we either use MRIs or CAT scans, 25% in other patients so 2 out of the 6 had significantly coded responses. Despite this modest activity, we have immediately noticed improvements in how the spleen felt, early satiety significantly dropped when we did mean comparisons from before the start until the end of the study. So that's something to look into to understand what this actually means, what is clinically relevant for patients, the objective measurements were not quite in concordance with what people reported subjectively, so that's something that's sparked more interest to our exploration. 

Very nice were exploratory endpoints or cytokines, they were measured dynamically throughout the study, prior to the infusion then prior every single infusion, so 6 times end of therapy and then 6 months follow-ups. We have seen very interesting results in drop of inflammatory cytokines that were quite elevated at the time of enrollment, keep in mind these patients were on ruxolitinib, which is the strongest JAK inhibitor to get rid of the cytokines. So that was one thing that we learned, that sub optimal responders have significantly increased information. We measured about 99 cytokines throughout the therapy and what we are showing at ASH is an extremely nice correlation of TGF beta with responders, so we have 5 patients that achieved some sort of response, including spleen symptoms or anemia benefits, and all of these cytokines decreased more than 50%. 
The same goes to the broad panel, where we illustrate in 1 patient that achieved SVR35 and TSS50. Here we are a little bit more looking at the rebalancing or remodulating of the immune system, which could be correlated with the disease pathogenesis reflected in our measurements and spleen symptoms because we show about one third of cytokines being completely downregulated, extreme drop, some of them are upregulated and some of them fluctuating all over the place prior to the infusions.

Of course, we have seen correlation with the deepest drop with the best responders, however there are some discrepancies with patients that would still have access extra subjective response and the cytokines were bouncing back and forward and then we had non responders that didn't even flinch. So that is something also to follow through there is more of this abstract this year on other drugs that [indiscernible] where cytokines matter, they do modulate the inflammatory mediator with these patients that are even significant on JAK inhibitors. 

In conclusion, we were actually showing that we could safely deliver at Tregs that are given in an outpatient setting as an add-on therapy, repeatedly cryopreserved 100 million cells a dose, 10 minutes outpatient, super quick, actually better than my transfusion dependency patients. We have not seen a significant concerns in terms of a safety, we have no need to do any HLA matching, cells are given without any cytoreductive therapies, so it's much faster, they are on demand, off the shelf.  Interesting improvements in symptoms, including significant decrease in fatigue and early satiety which was in a slight contrast with an immodest objective measurements of spleen volume reduction currently accepted endpoints. Cytokine panel that is going a bit more into it, the more analysis I’m going, that could indicate that we are rebalancing the immune system and we are hoping to learn more about what does this mean, what do we connect this with clinical relevance, and how do we more focus or basically move the needle and development of these diseases and their future.

Currently the study is open for expansion, which has changed the schedule because of the fluctuating cytokines and not quite understanding, is this dose enough for such significant inflammation at the beginning? So, the current expansion that's open include patients treated on the weekly basis times 4, and then monthly basis that's being currently done. There is currently approved 6 patients enrolled with the data reevaluation and analysis correlation, to see where this study can move forward, again it's only Phase 1 so we are just exploring the unexplored we are just learning what we haven’t learned before. 
 

Source:

Masarova L, Huang M, Goel S, et al. A Phase Ib, Open-Label Study of Add on Therapy with CK0804 in Participants with Myelofibrosis and Suboptimal Response to Ruxolitinib. Dec 7-10, 2024; San Diego, CA. Abstract: 999