The role of inherited genetic variants in rare blood cancer

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January 17, 2024

Researchers from the University of Cambridge, Wellcome Sanger Institute, and collaborators have shown how inherited genetic variants can influence the risk of developing a rare blood cancer.

Large-scale genetic analysis has helped researchers uncover the relationship between cancer-driving genetic mutations and inherited genetic variants in a rare type of blood cancer.

The team combined datasets to understand the impact of cancer-driving spontaneous mutations and inherited genetic variation on the risk of developing myeloproliferative neoplasms (MPN).

Published in Nature Genetics, the study describes how inherited genetic variants can influence whether a spontaneous mutation in a particular gene increases the risk of developing this rare blood cancer.

The analysis will have an impact on current clinical predictions of disease development in individuals.

More research is needed to understand the mechanisms behind how the inherited genetic variants influence the probability of developing rare blood cancer.

In the future, the work could aid drug development interventions that reduce the risk of disease.

Myeloproliferative neoplasms

MPNs are a group of rare and chronic blood cancers, with around 4,000 cases in the UK each year. These occur when the bone marrow overproduces blood cells, resulting in blood clots and bleeding.

MPNs can also progress into other forms of blood cancer.

Genetic risk score

There is a large amount of natural variation between individuals’ blood cells which can affect the amount of blood cells a person has and their traits. This is because different genes can influence blood cell features in an individual.

Researchers take known information about these genes during routine blood tests and analyse the variation to give a genetic risk score. This is how likely that individual is to develop a disease over their lifetime.

MPNs have been linked to random somatic mutations in a gene called JAK2; however, mutated JAK2 is commonly found in the global population. The vast majority of these individuals do not have or go on to develop MPN.

Previous studies identified over a dozen associated inherited genetic variants that increase the risk of MPN. However, these studies do not explain why most individuals do not go on to develop MPN.

Inherited genetic variants can influence risk

The new study combined information on the known somatic driver mutations in MPN inherited genetic variants, and genetic risk scores from individuals with MPN.

They found that the inherited genetic variants that cause natural blood cell variation in the population also impact whether a JAK2 somatic mutation will cause MPN. The team also discovered that individuals with an inherited risk of having a higher blood cell count could display MPN features in the absence of cancer-driving mutations, mimicking disease.

Dr Jing Guo, from the University of Cambridge and the Wellcome Sanger Institute and first author of the study, said: “Our large-scale statistical study has helped fill the knowledge gaps in how variants in DNA, both inherited and somatic, interact to influence complex disease risk.

“By combining these three different types of datasets we were able to get a more complete picture of how these variants combine to cause blood disorders.”

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Fedratinib Improves Myelofibrosis Management Compared With Ruxolitinib

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By Patrick Daly – Last Updated: January 17, 2024

Treatment with fedratinib, a Janus kinase inhibitor (JAKi), induced superior spleen volume reduction (SVR) and symptom response rates compared with best available therapy in patients with myelofibrosis (MF) who previously received ruxolitinib, according to data from the open-label phase III FREEDOM2 study, presented at the 65th American Society of Hematology Annual Meeting & Exposition.

“Most patients on best available therapy received ruxolitinib, highlighting a need for an alternative JAKi,” stated lead author of the study, Claire Harrison, MD, FRCP, from Guy’s and St. Thomas’ NHS Foundation Trust in London, England.

The FREEDOM2 trial enrolled patients aged 18 years or older with primary, post-polycythemia vera, or post-essential thrombocythemia MF with splenomegaly who were intolerant or refractory to, or relapsed after ruxolitinib. The primary endpoint was SVR ≥35% (SVR35) at the end of the sixth 28-day cycle.

Fedratinib for Myelofibrosis Treatment Superior to Ruxolitinib

In total, 201 patients were randomized to fedratinib (n=134) or best available therapy (n=67). The cohort had a median age of 70 (interquartile range, 64-74), 52.2% were male, 54.7% had primary MF, and 76.1% had a Dynamic International Prognostic Scoring System risk score of intermediate-2.

Overall, 70.1% of patients in the best available therapy arm received ruxolitinib, 10.4% received hydroxyurea, and 7.5% received ruxolitinib plus hydroxyurea. Additionally, 46 (68.7%) patients in the best available therapy arm crossed over to fedratinib after either disease progression or the sixth cycle response assessment.

With a median follow-up of 15 months at the data cutoff, researchers reported the fedratinib group had a significantly higher SVR35 rate of 35.8% at the end of cycle six compared with best available therapy at 6.0% (P<.0001). Fedratinib also yielded superior SVR ≥25% at the cycle six assessment and superior SVR35 at any point during treatment. The rate of symptom response at the end of cycle six was 34.1% with fedratinib versus 16.9% with best available therapy (P=.0033).

In short, “fedratinib demonstrated superior SVR and symptom response rates compared with [best available therapy]” in patients with MF and prior ruxolitinib treatment, concluded Dr. Harrison and colleagues.

Reference

Harrison CN, Mesa RA, Talpaz M, et al. Efficacy and safety of fedratinib in patients with myelofibrosis previously treated with ruxolitinib: results from the phase 3 randomized FREEDOM2 study. Abstract #3204. Presented at the 65th ASH Annual Meeting & Exposition; December 9-12, 2023; San Diego, California.

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CALR-Mutated Essential Thrombocythemia Associated With Higher Progression to Myelofibrosis Risk

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CALR mutations in essential thrombocythemia are associated with lower thrombosis risk and higher risk of progression to myelofibrosis (MF) compared with other driver mutations, according to a recent study.

The study was led by Katie Erdos, a Research Program Assistant at Weill Cornell Medicine’s Richard T. Silver, MD Myeloproliferative Neoplasms Center, and presented at the 65th American Society of Hematology Annual Meeting & Exposition.

Erdos and colleagues conducted the study to evaluate the impact of driver mutations on the risks of thromboembolic events, disease progression, and patient mortality.

Of 338 total patients, 216 (64%) were positive for JAK2V617F, 85 (25%) were positive for CALR, 19 (6%) were positive for MPL, and 18 were (5%) triple-negative (TN). Red cell parameters were slightly higher in patients with JAK2V617F mutations (P<0.001), white blood cell count was highest in TN patients (P=0.012), and platelet count did not significantly vary across mutation groups (P=0.064).

The 20-year thrombosis-free survival was 71% for JAK2V617F, 100% for CALR, 90% for MPL, and 83% for TN (P=0.0027). The 20-year MF-free survival was 87% for JAK2V617F, 48% for CALR, 65% for MPL, and 94% for TN (P=0.00053). Meanwhile, the 20-year overall survival was 76% for JAK2V617F, 86% for CALR, 89% for MPL, and 90% for TN (P=0.66).

“Our findings reinforce the need for long-term data to guide therapy for ET based not only on the near-term thrombotic risk, but also on the long-term risk of progression,” wrote Erdos and colleagues.

Reference

Erdos K, Lee N, Lebbe A, et al. Low thrombosis risk CALR mutations confer higher risk of essential thrombocythemia progression. Abstract #1819. Presented at the 65th ASH Annual Meeting & Exposition; December 9-12, 2023; San Diego, California.

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Inherited polygenic effects on common hematological traits influence clonal selection on JAK2V617F and the development of myeloproliferative neoplasms

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Jing Guo, Klaudia Walter, Pedro M. Quiros, Muxin Gu, E. Joanna Baxter, John Danesh, Emanuele Di Angelantonio, David Roberts, Paola Guglielmelli, Claire N. Harrison, Anna L. Godfrey, Anthony R. Green, George S. Vassiliou, Dragana Vuckovic, Jyoti Nangalia & Nicole Soranzo

Nature Genetics (2024)

Abstract

Myeloproliferative neoplasms (MPNs) are chronic cancers characterized by overproduction of mature blood cells. Their causative somatic mutations, for example, JAK2V617F, are common in the population, yet only a minority of carriers develop MPN. Here we show that the inherited polygenic loci that underlie common hematological traits influence JAK2V617F clonal expansion. We identify polygenic risk scores (PGSs) for monocyte count and plateletcrit as new risk factors for JAK2V617F positivity. PGSs for several hematological traits influenced the risk of different MPN subtypes, with low PGSs for two platelet traits also showing protective effects in JAK2V617F carriers, making them two to three times less likely to have essential thrombocythemia than carriers with high PGSs. We observed that extreme hematological PGSs may contribute to an MPN diagnosis in the absence of somatic driver mutations. Our study showcases how polygenic backgrounds underlying common hematological traits influence both clonal selection on somatic mutations and the subsequent phenotype of cancer.

Main

Myeloproliferative neoplasms (MPNs) are rare chronic hematological cancers characterized by the overproduction of mature blood cells leading to elevated blood cell parameters. They are typically driven by somatically mutated JAK2-mediated, calreticulin (CALR)-mediated or MPL-mediated clonal expansion1. JAK2 mutations are found in both polycythemia vera (PV) and essential thrombocythemia (ET), which are distinct but overlapping MPNs characterized by increased numbers of red blood cells and platelets, respectively. Mutant JAK2 is commonly detectable in 0.1–3% of the healthy population as clonal hematopoiesis (CH)2,3,4,5,6,7, with the vast majority of carriers not meeting or going on to develop disease-defining characteristics of MPN. Little is understood about why only a minority of individuals with mutated JAK2 develop more severe hematological manifestations of MPN and the factors that influence blood count heterogeneity in MPNs.

The 46/1 haplotype near JAK2 is a known germline risk factor for MPNs in the population8. Genome-wide association studies (GWAS) have identified additional disease-associated germline risk loci, estimating the liability-scale heritability of MPNs based on common single-nucleotide polymorphisms (SNPs) to be ~6.5% (refs. 9,10,11). However, these germline risk loci insufficiently explain the phenotypic heterogeneity observed within MPNs and in JAK2-mutated healthy carriers.

Blood cell traits vary widely in the healthy population. The genetic architecture underlying these traits is highly polygenic, with more than 11,000 independently associated genetic variants discovered so far12,13,14. These genome-wide associated variants, when combined in polygenic scores (PGSs), explain a large proportion of phenotypic variance among healthy individuals (from 2.5% for basophil count to 27.3% for mean platelet volume) and are associated with multiple common diseases and rare hematological disorders14. We hypothesized that a genetic burden of germline variants associated with extreme hematological traits could influence phenotypic heterogeneity in association with mutated JAK2, by influencing the clonal dynamics of mutant JAK2 and/or modifying its downstream consequences. In this study, we integrate information on somatic driver mutations, germline genetic variants associated with MPNs, and CH and hematological trait PGSs to study how inherited polygenic variation underlying blood cell traits influences clonal selection on mutated JAK2 and MPN disease phenotypes (Supplementary Fig. 1).

Results

Inherited polygenic contribution to JAK2 V617F positivity

One in 30 healthy individuals reportedly harbors JAK2V617F in their blood, as determined using sensitive assays6. The majority of such individuals have low levels of JAK2V617F and do not meet clinical criteria for MPN due to the absence of elevated blood cell parameters. We wished to understand whether inherited polygenic loci that underlie blood cell traits influence the strength of clonal selection on JAK2V617F.

We studied the germline characteristics of individuals in UK Biobank (UKBB) with and without JAK2V617F. From 162,534 genetically unrelated individuals of European ancestry within the UKBB whole-exome sequencing cohort (‘200k UKBB-WES cohort’; Methods), we identified 540 individuals with one or more mutant reads for JAK2V617F (0.3%, median variant allele frequency (VAF) = 0.056, range = 0.019–1; Supplementary Fig. 2; ‘UKBB-JAK2V617F cohort’). The lower rate of JAK2V617F in the UKBB-WES cohort compared to other population studies6,7 could be explained by its low sequencing coverage (21.5× depth), as also reported previously15 (Supplementary Fig. 3). As expected, there was some overlap among individuals with JAK2V617F and those with a diagnosis of MPN. Of the 423 individuals labeled with a diagnosis of MPN (156 with ET, 161 with PV and 106 with myelofibrosis (MF)), 72 were positive for JAK2V617F (Supplementary Table 1).

We built PGSs for 29 blood cell traits covering a wide range of hematopoietic parameters (Supplementary Table 2). Blood cell trait-specific PGSs were then weighted (by effect size) by the sum of all common (minor allele frequency (MAF) > 0.01) variants that were independently associated with a blood cell trait at genome-wide significance (P < 5 × 10−8) in UKBB (Methods)14. To assess the association between hematological PGSs and small (VAF < 0.1, n = 397) or large (VAF ≥ 0.1, n = 143) JAK2V617F clones, we used multinomial logistic regression including PGSs for each hematological trait (units of s.d.), together with previously reported germline sites associated with MPN9 and CH16 (PGSMPN and PGSCH) as covariates. To account for the recognized predisposition risk for MPN driven by the JAK2 46/1 haplotype8, we computed two PGSMPN scores, separating rs1327494 (tagging the JAK2 46/1 haplotype; PGSMPN–46/1) from nontagging JAK2 variants (PGSMPN-other). We found a negative association between the PGSs for both mean reticulocyte volume (PGSMRV) and immature reticulocyte fraction (PGSIRF) and small JAK2V617F clones (P = 6.2 × 10−4 and 0.0018, false discovery rate (FDR) < 0.05; Supplementary Table 3). We also found significant positive associations with small JAK2V617F clones for the PGSs of plateletcrit (PGSPCT) and monocyte count (PGSMONO) (P = 9.5 × 10−4 and 0.0036, FDR < 0.05). Germline predisposition to high MONO and PCT values was also positively associated with large JAK2V617F clones at modest significance (P = 0.033 and 0.0022, FDR-adjusted P = 0.31 and 0.064; Fig. 1a). Repeating the analysis above excluding MPN cases still demonstrated a significant association between PGSPCT or PGSMONO and small JAK2V617F clones (P < 0.013, Bonferroni corrected; Supplementary Table 4), suggesting that the inherited effects on JAK2V617F were not driven by the subset of MPN cases. These associations were independent of the known germline risk loci associated with MPN and CH (Supplementary Table 3). Validating these associations in the full UKBB-WES dataset (n = 799 and 326 for small and large clones, respectively, and n = 338,919 for controls), we again replicated the associations between PGSPCT and small JAK2V617F clones and between PGSMONO and large JAK2V617F clones at FDR < 0.05 (PCT: odds ratio (OR) = 1.15 (change in odds per increase of 1 s.d. in PGS), 95% confidence interval (CI) = 1.07–1.24, P = 1.4 × 10−4; MONO: OR = 1.20, 95% CI = 1.07–1.34, P = 0.0014; Supplementary Table 5).

Data are presented as ORs (solid dots) with 95% CIs (error bars). a, PGSs with significant associations with small clone size of JAK2V617F (FDR < 0.05) compared to the CH and MPN PGSs (Supplementary Table 3). OR was defined as the change in odds per increase of 1 s.d. in PGS. b, Causal effects estimated by four MR methods for the exposure traits whose PGSs were found to have significant predisposition risk for JAK2V617F positivity (Supplementary Table 7). OR was defined as the change in odds per increase of 1 s.d. in exposure. The MR results shown were based on GWAS summary statistics for JAK2V617F positivity in the full UKBB (Supplementary Fig. 4). Results based on the main discovery set (200k UKBB-WES cohort) are shown in Supplementary Table 6. The MR result for MRV was not available due to a lack of corresponding GWAS summary data in INTERVAL.

To understand the causal relationship among these associations, we undertook Mendelian randomization (MR) analyses with GWAS estimates for the exposure (blood traits) and the outcome (JAK2V617F positivity; Supplementary Fig. 4) obtained from two independent sources. We used genetic instruments for hematological traits identified from UKBB, with effect size estimates from INTERVAL17 (n = 30,305), an external independent cohort. MRV was excluded due to a lack of data in INTERVAL. Both PCT and MONO showed significant causality on the presence of a JAK2V617F clone based on inverse variance-weighted (IVW)18 MR and demonstrated consistent effect estimates using two other MR methods (simple median and weighted median), suggesting that higher MONO and higher PCT values cause a detectable JAK2V617F clone (Supplementary Table 6).

Extending this analysis to the full UKBB-WES cohort (JAK2V617F, n = 1,125; controls, n = 338,919) validated these causal associations with greater estimation accuracy (PCT: ORIVW = 1.52, 95% CI = 1.29–1.78, P = 3.0 × 10−7; MONO: ORIVW = 1.3, 95% CI = 1.15–1.49, P = 4.6 × 10−5; Fig. 1b and Supplementary Table 7). The IVW method of MR (Methods) assumes that the germline loci that drive MONO and PCT have no direct causal effect on driving a JAK2V617F clone (that is, there are no direct causal effects of the genetic instruments on the outcome). We found no evidence of pleiotropy using the MR-Egger19 test; the estimated intercept was not significantly different from zero with P = 0.84 and P = 0.90 for PCT and MONO, respectively. The causal relationship was also significant for PCT and MONO (P < 0.05; Supplementary Table 7 and Supplementary Fig. 5). Additionally, the estimates were not biased by any potential pleiotropic outlier variants and were highly consistent with outlier-corrected causal estimates (Supplementary Table 7 and Methods). Lastly, to ensure the results were not confounded by the possibility that the genetic loci used as instruments for MR directly promoted the outcome (that is, JAK2V617F positivity), we repeated the analysis excluding genetic instruments associated with JAK2V617F positivity (Passociation < 10−6), as well as those that correlated with JAK2V617F variants (that is, those variants and JAK2V617F variants are in linkage disequilibrium (LD) r2 > 0.01) or were in proximity to JAK2V617F variants (in the 10-Mb region centered on each variant), and found no major changes (Supplementary Table 8). Importantly, any reverse causal effect we detected for MONO and PCT was subtle and with pleiotropic effects (PEgger > 0.05 and PEgger-intercept < 0.05; Supplementary Table 9 and Supplementary Fig. 6).

Overall, the association results combined with MR suggest that higher PCT and MONO are causal for the presence of a JAK2V617F clone. This would also explain why individuals with germline predisposition to high PCT and MONO are also more likely to harbor a JAK2V617F clone. Given that acquisition of somatic mutations in blood is largely stochastic in healthy populations20, our data suggest that genetically predicted PCT and MONO influence clonal selection on nascent JAK2V617F cells to promote mutation acquisition.

Germline contribution to blood cell count variation in MPNs

Having shown that polygenic germline loci can predispose to JAK2 clone positivity through their influence on blood cell trait levels, we next studied the contribution of these inherited sites to clinical phenotypes of MPN. We first considered the four blood cell traits that are used to define MPN subcategories clinically21 as follows: hemoglobin concentration (HGB) (g dl–1 divided by 10), hematocrit (HCT) (%), platelet count (PLT) (×109 divided by 1,000) and white blood cell count (WBC) (×109 divided by 100). We used SNP arrays to measure genome-wide polymorphism in an MPN cohort of 761 patients (PV, n = 112; ET, n = 581; MF, n = 68), in whom diagnostic blood cell counts were available and mutation status for a panel of cancer-associated genes (Fig. 2a) had previously been characterized22.

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GB2064 Displays Preliminary Efficacy, Tolerability in Myelofibrosis

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January 16, 2024

Kyle Doherty

The potential first-in-class, oral, lysyl oxidase-like 2 (LOXL2) inhibitor GB2064 displayed efficacy with a generally acceptable tolerability profile in the treatment of patients with myelofibrosis, according to topline findings from the phase 2a MYLOX-1 trial (NCT04679870).1

Among evaluable patients with myelofibrosis who were treated with GB2064 monotherapy for a minimum of 6 months (n = 10), 6 experienced a reduction in collagen fibrosis of the bone marrow of at least 1 grade. All patients who achieved this reduction in bone marrow fibrosis displayed stable hematological parameters, including hemoglobin, white blood cell count, and platelet count. This indicates the agent’s potential impact on disease progression and disease-modifying capabilities. At 6 months of treatment, 1 patient experienced a reduction in spleen volume of at least 35%, 2 reduced their Total Symptom Score (TSS) by over 50%, and another patient experienced an anemia response.

“It is exciting and encouraging to see that the data from the MYLOX-1 trial affirms the safety and effectiveness of LOXL-2 inhibition in the challenging landscape of myelofibrosis,” Claire Harrison, MD, FRCP, FRCPath, chair of the Safety Review Committee for the MYLOX-1 trial, a professor of myeloproliferative neoplasms, and the clinical director of Guy’s and St Thomas’ NHS Foundation Trust in London, England, said in a press release. “I am especially intrigued by the unique observed improvements in bone marrow collagen fibrosis, showcasing the targeted impact on a crucial aspect of this relentless disease.”

MYLOX-1 was an open-label, single-arm study that enrolled adult patients with primary or secondary myelofibrosis who were ineligible, refractory, or intolerant to treatment with a JAK inhibitor. Patients had intermediate-2 or high-risk disease by the Dynamic International Prognostic Scoring System-plus, or low-risk disease with symptomatic splenomegaly. Eligible patients were also required to have an ECOG performance status of 2 or less, not be receiving JAK inhibitor therapy, display required baseline laboratory counts, and have a documented history of transfusion records in the preceding 12 weeks to day 1 of study treatment.2

All patients on the study treatment received 1000 mg of oral GB2064 twice daily for 9 months. Patients underwent bone marrow biopsies at the beginning of the trial and again at 3, 6 and 9 months. The primary end point was the safety and tolerability of GB2064; key secondary end points included evaluating hematological parameters and the direct anti-fibrotic activity of GB2064 by blocking LOXL2 in an indication that allows for repeated tissue biopsies.1,2

The study dosed a total of 18 patients with myelofibrosis. Most patients (61%) had previously received the JAK inhibitor ruxolitinib (Jakafi); 8 of these patients were refractory to JAK inhibitor therapy and 3 were intolerant.1

Additional assessment of bone marrow biopsies in MYLOX-1 revealed that GB2064 penetrated the bone marrow and could exert its anti-fibrotic effect directly in the disease compartment. Additionally, the agent displayed systemic target engagement by binding to LOXL2 in plasma. Four patients who experienced clinical benefit with GB2046, as determined by the treating physician, have entered the extension phase of MYLOX-1. Notably, 1 of these patients has received treatment for over 30 months.

GB2064 displayed a tolerable safety profile, with 8 of the 18 dosed patients completing treatment in the core phase of MYLOX-1. The remaining 10 patients discontinued treatment due to adverse effects or progressive disease. The most common any-grade treatment-related adverse effects were manageable with standard therapy and gastrointestinal in nature. The lone treatment-related serious adverse effect was a case of fall, which was determined to be possibly related to GB2064 treatment.

“We believe that the topline results from the MYLOX-1 trial reaffirm the anti-fibrotic activity observed in the intermediate assessment of the trial announced in September 2022,” Hans T. Schambye, MD, PhD, the president and chief executive officer of Galecto, said in the press release. “We are very excited with the proof of principle achieved with GB2064, showcasing its strong anti-fibrotic impact in a very challenging patient population. The encouraging topline results from the MYLOX-1 trial reinforce our confidence in GB2064’s potential as a transformative therapy for various cancers and a range of fibrotic diseases, but we will not make any decisions relating to funding additional trials with GB2064 until we complete our previously announced strategic alternative process.”

In September 2023, Galecto announced that it completed a review of its business and would conduct a comprehensive exploration of strategic alternatives focused on maximizing shareholder value. Galecto did not set a timetable for completion of the evaluation and said it did not intend to disclose further developments or guidance on the status of its programs unless it determined that further disclosure is appropriate or necessary.3

References

  1. Topline results from MYLOX-1 trial demonstrate reduction in fibrosis of the bone marrow in patients with myelofibrosis. News release. Galecto, Inc. December 21, 2023. Accessed January 16, 2024. https://www.biospace.com/article/releases/topline-results-from-mylox-1-trial-demonstrate-reduction-in-fibrosis-of-the-bone-marrow-in-patients-with-myelofibrosis/
  2. A study to evaluate the safety, tolerability, pharmacokinetics and pharmacodynamics of oral GB2064 in participants with myelofibrosis. ClinicalTrials.gov. Updated May 6, 2023. Accessed January 16, 2024. https://clinicaltrials.gov/study/NCT04679870
  3. Galecto announces plans to explore strategic alternatives. News release. Galecto, Inc. September 26, 2023. Accessed January 16, 2024. https://ir.galecto.com/news-releases/news-release-details/galecto-announces-plans-explore-strategic-alternatives

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INCA-033989 by Incyte for Myelofibrosis: Likelihood of Approval

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January 12, 2024

INCA-033989 is under clinical development by Incyte and currently in Phase I for Myelofibrosis. According to GlobalData, Phase I drugs for Myelofibrosis have an 86% phase transition success rate (PTSR) indication benchmark for progressing into Phase II. GlobalData’s report assesses how INCA-033989’s drug-specific PTSR and Likelihood of Approval (LoA) scores compare to the indication benchmarks.

GlobalData tracks drug-specific phase transition and likelihood of approval scores, in addition to indication benchmarks based off 18 years of historical drug development data. Attributes of the drug, company and its clinical trials play a fundamental role in drug-specific PTSR and likelihood of approval.

INCA-033989 overview

INCA-033989 is under development for the treatment of myelofibrosis (MF), essential thrombocythemia (ET). The drug candidate is a monoclonal antibody which acts by targeting calreticulin (CALR).

It was also under development for post-essential thrombocythemia myelofibrosis (Post-ET MF) and primary myelofibrosis (PMF).

Incyte overview

Incyte is a biopharmaceutical company, which discovers, develops and commercializes proprietary cancer therapeutics. The company’s lead product, Jakafi (ruxolitinib) is marketed in the US for the treatment of patients with high-risk myelofibrosis; and polycythemia vera who are intolerant to hydroxyurea. The company distributes Jakafi through a network of specialty pharmacy providers and wholesalers. In collaboration with Incyte, Novartis International Pharmaceutical Ltd (Novartis) develops and commercializes ruxolitinib outside the US for hematologic and cancer indications under the name Jakavi. The company’s pipeline portfolio encompasses drugs for the treatment of lung cancer, graft versus host disease, b-cell malignancies, solid tumors, non-small cell lung cancer, glioblastoma, liver cancer, and advanced malignancies. Incyte is headquartered in Wilmington, Delaware, the US.

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Transfusion Independence With Momelotinib Impacts OS in Myelofibrosis

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Targeted Oncology Staff

DISCUSSION QUESTION

  • How do the most recent data on Janus kinase (JAK) inhibitors support/change your approach to treating patients?​

DRAUPADI TALREJA, MD: I’m all for momelotinib [Ojjaara]. I was never for ruxolitinib [Jakafi] but there was nothing else available, so I used it.

HARIS ALI, MD: Would you use momelotinib in the majority of your patients or just on certain patients with moderate or severe anemia?

TALREJA: I will use it for them because it reduces the spleen anyway; all [JAK inhibitors] reduce the spleen beautifully. Because it does not cause anemia and can make them transfusion independent, if they have symptoms, a big spleen, and anemia, I have many reasons to use momelotinib. So I’m going to go there, and I’m going to [use less] ruxolitinib.

ALI: Maybe the once-daily dose might be helpful as well.

ARATI CHAND, MD: Was the SIMPLIFY-1 study [NCT01969838] powered for superiority or noninferiority?

ALI: It was powered for noninferiority for [spleen volume reduction] and symptoms, and superiority for the transfusion independence.1

CHAND: What about the adverse event [AE] profile?

ALI: Ruxolitinib has a bit more thrombocytopenia and anemia, and momelotinib has some more gastrointestinal [AEs] and nausea. Otherwise, they were quite comparable.1

CHAND: It looks less toxic compared with ruxolitinib. I would probably change and start using more momelotinib now that is available. Earlier, we didn’t have anything except ruxolitinib and fedratinib [Inrebic]. Pacritinib had such a restricted indication that you could only use it for those patients with very thrombocytopenic myelofibrosis. I think I would definitely start my new patients on momelotinib.

ALI: Would that be regardless of the hemoglobin and platelet count?

CHAND: I think so. It looks like it’s better tolerated. Patients are different, so there may be patients who don’t tolerate this. But in that case, it would make sense to switch and see if they tolerate ruxolitinib better. Efficacy is one thing, but tolerance is also important, especially for treatments that have to be given over prolonged periods of time.

GEORGE HAJJAR, MD: The dosing is also an issue. Adjusting the dose of ruxolitinib is very frequent, depending on the platelet count and hemoglobin level. It’d be interesting to know how many patients got the full dosing of ruxolitinib in that trial vs momelotinib.

ALI: The correct dosing is also important, but it usually goes by the package insert, like 20 mg [twice daily ruxolitinib] for patients with greater than 200 × 109/L platelets, or [15 mg twice daily for patients with between 100 × 109/L and 200 × 109/L platelets].2

HAJJAR: Dose adjustments are always frequent. If we see platelet count drop, we have to tell the patient to decrease the dose, which will be a pain.

ALI: [In the COMFORT-I trial (NCT00952289)], although anemia was a big factor, discontinuation of ruxolitinib because of anemia was in less than 1% of the patients.3 Regardless, patients felt better with the improvement in the symptoms and the spleen symptoms. For whatever reason, that was not the one of the common reasons for discontinuation. I think one of the most common was thrombocytopenia; it wasn’t anemia.

One thing with momelotinib is that it has a lot of drug interactions with OATP1B1/B3 inhibitors, including with statins and different drugs.4 It’s something to watch out for, because hepatic dysfunction was another reason for the hold and [we need to] look at it further. Drug interactions may be the one thing to look out for in a patient, as most of the patients over 65 will be on 5 or 6 different medication for different comorbidities.

CHAND: Was that interaction only for 1 statin or for all statins? Because [many patients] are on a statin now.

ALI: That’s right, so dose reduction might be needed for the statins. There’s a whole drug list with OATP1B1/B3 inhibitors, so you just have to watch for that, but it has more than 1 statin listed there.

DISCUSSION QUESTION

  • How do the overall survival (OS) data influence your choice of therapy?​

ALI: We looked into an OS advantage with ruxolitinib.5 We don’t have too much survival data with [momelotinib] but we do have with the transfusion independence vs non-independence.6 How does that affect your therapy?

TALREJA: I think OS [could be] better with momelotinib. With ruxolitinib, the only good thing is they feel good. It’s their quality of life that helps them live longer. I don’t think ruxolitinib does anything to the bone marrow to reduce the myelofibrosis, so I think momelotinib is a much better drug.

ALI: Would everyone say the same thing about momelotinib for OS compared with other JAK inhibitors including ruxolitinib?

CHAND: I don’t know if you can say that momelotinib has superior OS [based on the trials], but it is basically dependent on transfusion burden. Regardless of what medication you are on, if you’re transfusion dependent, your survival is poor, and if you’re transfusion independent, you’re going to do better in the long run.

ALI: You’re right. Anemia is a big [factor]; if we’ll look at the HR…among all the other risk factors like age or low platelet count, anemia is the biggest factor and transfusion dependence [is based on] patients who are more anemic, so there is definitely poorer survival in those patients.

SWARNA CHANDURI, MD: Is this because this drug works on the hepcidin as an inhibitor? Is that the reason why this is better tolerated and [leads to] less dependence on the transfusions?

ALI: Yes, [inhibiting] the hepcidin pathway, and further reduction to ACVR1 leads to [transfusion independence].7

CHANDURI: If this drug has the additional quality of [ruxolitinib] and improving it, then it is a better drug than ruxolitinib. But the main thing is that is why patients with anemia do better.

References:

1. Mesa RA, Kiladjian JJ, Catalano JV, et al. SIMPLIFY-1: A Phase III randomized trial of momelotinib versus ruxolitinib in Janus kinase inhibitor-naïve patients with myelofibrosis. J Clin Oncol. 2017;35(34):3844-3850. doi:10.1200/JCO.2017.73.4418

2. Jakafi. Prescribing information. Incyte; 2021. Accessed December 18, 2023. https://tinyurl.com/3t6dd8jj

3. Verstovsek S, Mesa RA, Gotlib J, et al. A double-blind, placebo-controlled trial of ruxolitinib for myelofibrosis. N Engl J Med. 2012;366(9):799-807. doi:10.1056/NEJMoa1110557

4. Ojjaara. Prescribing information. GlaxoSmithKline; 2023. Accessed December 18, 2023. https://tinyurl.com/4wc5dmet

5. Verstovsek S, Gotlib J, Mesa RA, et al. Long-term survival in patients treated with ruxolitinib for myelofibrosis: COMFORT-I and -II pooled analyses. J Hematol Oncol. 2017;10(1):156. doi:10.1186/s13045-017-0527-7

6. Mesa R, Harrison C, Oh ST, et al. Overall survival in the SIMPLIFY-1 and SIMPLIFY-2 phase 3 trials of momelotinib in patients with myelofibrosis. Leukemia. 2022;36(9):2261-2268. doi:10.1038/s41375-022-01637-7

7. Oh ST, Talpaz M, Gerds AT, et al. ACVR1/JAK1/JAK2 inhibitor momelotinib reverses transfusion dependency and suppresses hepcidin in myelofibrosis phase 2 trial. Blood Adv. 2020;4(18):4282-4291. doi:10.1182/bloodadvances.2020002662

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Tamoxifen Reduces Allele Burden of Patients With Myeloproliferative Neoplasms

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Vicki Moore, PhD

In a clinical trial evaluating the use of tamoxifen in patients with stable myeloproliferative neoplasms (MPNs), 3 patients showed a 50% or greater reduction in mutant allele burden at 24 weeks. This and other results from the study appeared to support further investigation of this agent in this population, but with consideration of possible thrombotic risk. Study results were reported in the journal Nature Communications.

The study’s primary endpoint was a ≥50% reduction in the mutant allele burden in peripheral blood at 24 weeks, with trial success involving at least 3 patients having met this outcome. Several secondary and exploratory outcomes were also evaluated.

These results warrant further investigation of tamoxifen as potential therapeutic for MPN in larger studies, after careful consideration of the risk of thrombosis.

There were 38 patients recruited into the study, with 32 patients completing 24 weeks of treatment. In the total population of 38 patients, 36.8% had essential thrombocythemia, 28.9% had polycythemia vera, 15.8% had primary myelofibrosis, 13.2% had post-polycythemia vera myelofibrosis, and 5.3% had post-essential thrombocythemia myelofibrosis. The overall population had a mean age of 66.3 years (range, 50.0-87.0 years).

There were 3 patients who reached the primary outcome of a ≥50% reduction in mutant allele burden at 24 weeks. Therefore, this study was considered a success in terms of its primary outcome. An additional 5 patients met a secondary outcome of achieving a ≥25% reduction in mutant allele burden, of whom 3 patients had JAK2V617F mutations.

The study investigators additionally performed analyses using hematopoietic stem/progenitor cells that revealed distinctive molecular signatures in responders and nonresponders at baseline. In responders, increased expression of genes associated with JAK-STAT signaling and oxidative phosphorylation appeared to become downregulated in the presence of tamoxifen.

References: Fang Z, Corbizi Fattori G, McKerrell T, et al. Tamoxifen for the treatment of myeloproliferative neoplasms: a phase II clinical trial and exploratory analysis. Nat Commun. 2023;14(1):7725. doi:10.1038/s41467-023-43175-5

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Stumbling Through PV

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“Even if you stumble, you are still moving forward.” This is my go-to quote when life’s difficulties arise. Hearing the words, you’ve got cancer
multiple times will make you feel like you are stumbling through life. The question is how do you stop the feeling of stumbling through a
cancer diagnosis?

In November 2017, I came back from a 200-mile bike ride and felt a little more fatigued and weak than usual. My platelets were in the high 700 range. Docs initially thought this was from inflammation from my bike ride. After a number of blood tests and a bone marrow biopsy, I was initially diagnosed with Essential Thrombocytosis. My diagnosis changed two years ago to Polycythemia Vera. In retrospect, I truly believe I was having symptoms long before my diagnosis. Learning how to manage your symptoms takes a lot of trial and error and patience. Being open to making a little change in your daily routine here and there to manage some of your symptoms is really helpful. When you try something different, write down the change and try that change for a week or so. If the change works for you, move forward. If not, try to find another little tweak of change to help you with your symptoms.

Some of my most challenging symptoms initially were itchy skin, fatigue, and gut issues. Some tweaks to my daily routine such as increased hydration, tweaking of my diet, taking lukewarm & quick showers, and being active most days, have really helped me. Additionally, my current medications and an occasional phlebotomy have really helped manage most of my symptoms. On a day when your symptoms are challenging, just give yourself some grace and relax. Remember as we age, not every little symptom we experience is related to our MPNs.
Finally, a cancer journey is never easy and can feel like you are stumbling through life. When you stumble, you have to learn how to get back up and move on which can be challenging. For me, my attitude about my PV diagnosis now is, that this is just a little stumble on life’s road. That helps me move forward and focus on living every day in this journey called life.

JBI-802 initial Phase I data suggests therapeutic potential in sensitizing immunotherapy resistant tumors and in Myeloproliferative Neoplasms with thrombocytosis

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BEDMINSTER, N.J., Jan. 8, 2024 /PRNewswire/ — Jubilant Therapeutics Inc., a clinical-stage biotechnology company pioneering the development of a first-in-class CoREST (Co-repressor of Repressor Element-1 Silencing Transcription) inhibitor JBI-802 with the dual activity on LSD1 and HDAC6, today announced preliminary safety, pharmacokinetic and initial efficacy results of the Phase I trial in advanced cancer patients. Furthermore, the study results provide a human proof of principle for expanding the development of JBI-802 in Essential Thrombocythemia (ET) and related Myeloproliferative Neoplasms (MPN/MDS) with thrombocytosis.

The data from first 11 patients with advanced cancer revealed a dose-proportional increase in exposure across cohorts and a strong correlation between the exposure and the on-target effects of platelet decrease, indicating that pharmacological relevant level of LSD1 inhibition have been achieved. At the same time, platelet decrease is the only adverse event above grade 1 observed in these patients, which differentiates JBI-802 from LSD1-only inhibitors. Specifically, no AEs (Adverse Events) of anemia has been observed, which is potentially due to the positive benefit of inhibition of HDAC6 in erythrocytes. Also, there are no reports of Dysgeusia, an adverse event that has been observed with LSD1-only inhibitors.

Among the 11 patients, two were NSCLC (Non-small Cell Lung Cancer) patients, both had progressed on doublet immunotherapy, nivolumab+ipilimumab as first line treatment and both showed anti-tumor activity. Both the patients were treated at lower dose level (10mg) where no relevant decrease of platelets is seen, suggesting that in patients with sensitive tumors this dose can be pharmacologically active with a desirable safety profile.

Both NSCLC patients had failed first line treatment with doublet immunotherapy, nivoluman/ipilumab prior to enrolling in the JBI-802 study. The first patient had a STK11 mutation, known to decrease the effectiveness of immunotherapy, present in around 10% of NSCLC patients (higher frequency in lung adenocarcinoma). JBI-802 showed a confirmed partial response in this IO-refractory NSCLC patient with a 39% decrease in the target lung tumor mass. The tumor shrinkage outcome was accompanied by a complete resolution of pancoast syndrome (lung lesion affecting the nerves of brachial plexus). The response appears to be durable after nine cycles and the patient remains on JBI-802 therapy.

The second patient had both lung lesion and liver metastasis, which are known to confer resistance to immunotherapy and lead to poor prognosis. Treatment with JBI-802 resulted in over 50% shrinkage of the patient’s liver metastasis and a complete resolution of related portal hypertension, edema and improvement of quality of life.

Dr. Alexander Starodub, The Christ Hospital – Cincinnati, treating physician for the above patients commented, “The anti-tumor activity seen in these two NSCLC patients is remarkable given the poor prognosis based on their genetic and metastatic pattern. The 10 mg dose of JBI-802 was well-tolerated without any clinically significant adverse effects and the initial clinical data suggest a good therapeutic index for JBI-802.”

Preclinical studies showed a synergistic anti-tumor effect by combining immunotherapy and JBI-802 in xenograft models. In addition, the CoREST inhibition was reported to sensitize immunotherapy resistant tumors, especially those with STK11 mutations. Taken together, the preliminary efficacy data from the JBI-802 Phase I study suggest the opportunity that a combination between immunotherapy and JBI-802 could bring a new therapy option to such patient populations with limited treatment options.

In addition, the on-target dose/exposure-proportional decrease in platelet constitute a proof-of-principle that JBI-802 can be an active compound in hematological malignancies like Essential Thrombocythemia (ET) and other MPN/ MDS characterized by thrombocytosis. A follow up Phase I/II study in MPN/ET and MPN/MDS with thrombocytosis is being planned in the first quarter of this year to investigate JBI-802 as potential novel treatment option.

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