Pathophysiology of ANKRD26-related thrombocytopenia and B-ALL recurrence after blinatumomab

Summary

Blood Podcast Episode Summary

Podcast: Blood Podcast by the American Society of Hematology
Episode: Pathophysiology of ANKRD26-related thrombocytopenia and B-ALL recurrence after blinatumomab
Date: April 23, 2026
Host: Dr. Laurie Sen, Associate Editor
Guests:

• Dr. Shenguan Calvin Lee, Army Medical University, China
• Dr. Hrishi Krishna Srinagesh, Stanford University

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Episode Overview

This episode features in-depth expert conversations on two recent landmark studies published in Blood.

1. Mechanistic insights into ANKRD26-related thrombocytopenia using single cell profiling (with Dr. Shenguan Calvin Lee)
2. Real-world outcomes of CAR T-cell therapy in B-ALL after blinatumomab exposure (with Dr. Hrishi Krishna Srinagesh)

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Segment 1: Pathophysiology of ANKRD26 Thrombocytopenia

Article: “Single cell profiling of ANKRD26 thrombocytopenia reveals progenitor expansion and polyploid apoptosis via Jun B P21”

Background and Motivation

• ANKRD26-related thrombocytopenia is an extremely rare, inherited platelet disorder caused by mutations in regulatory regions of the ANKRD26 gene.
  • “Patients typically have chronically low platelet counts and increased risk of bleeding. What makes this disease … difficult to study is the biology of megakaryocytes—they are rare, fragile, and highly heterogeneous.” – Dr. Lee [01:16]
• Earlier studies lacked cellular resolution; the aim was to achieve a high-definition understanding using single cell transcriptomics.

Methodology & Research Approach

• Used single cell transcriptome profiling of tens of thousands of individual cells from patients and controls
• Integrated these datasets with functional validation experiments
• Mapped the full developmental trajectory of megakaryocytes to identify where and why platelet production fails

Key Findings

• Two Major Abnormalities Observed:
  • Expansion of megakaryocyte progenitors: Early precursors increased in number
  • Failure of mature, polyploid megakaryocyte survival: Cells destined to produce platelets underwent premature apoptosis
• Underlying Mechanism Identified:
  • Overexpression of ANKRD26 activated the p21 pathway, driving apoptosis independently of the classical p53 pathway
  • “This provided first unified molecular explanations for platelet deficiency in this condition.” – Dr. Lee [04:10]

Therapeutic Implications

• Redefines the disease as a selective survival failure of mature megakaryocytes
• The p21 pathway becomes a target for future therapies
  • “If we can modulate this pathway, it may be possible to preserve polypoid megakaryocyte and improve platelet production.” – Dr. Lee [05:22]
• Broader impact: Demonstrates the power of single cell technologies in decoding rare hematologic diseases

Disease Complexity and Future Directions

• Mechanisms might also inform the risk of myeloid malignancies noted in ANKRD26 disorders [06:19]
• Need for expansion: Only ~300 patient pedigrees worldwide, so adding more is essential for broader findings
  • “Expanding the cohort would be helpful … mapping out the whole pathways and then we can figure out the molecular cellular mechanisms.” – Dr. Lee [07:21]

Next Research Questions

• Can pharmacological maturation halt apoptosis and enhance platelet production?
• Need for in vivo studies and clinical trials to validate findings [08:11]

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Segment 2: Outcomes of CAR T-Cell Therapy Following Blinatumomab in B-ALL

Article: “Blinatumomab Non-response Correlates with Poor Survival after Brexucabtagene”

Background: Immunotherapy Sequencing in B-ALL

• Multiple therapies (bispecific T cell engagers, CAR-T) now exist for relapsed/refractory B-ALL, all targeting CD19
  • “These include CD19 downregulation and T cell exhaustion … similar core prognostic markers for both treatment approaches like high disease burden.” – Dr. Srinagesh [10:14]
• Clinical concern: How should these therapies be sequenced?

ROCA Consortium & Study Aim

• ROCA (Real World Outcomes Collaborative for CAR T cells in Adult ALL):
  • 41 US centers; provides real-world outcomes data after Brexucabtagene (Brexocel) CAR T therapy
• The study aimed to assess whether and how prior blinatumomab exposure impacts CAR T-cell outcomes [11:24]

Study Design and Findings

• Large retrospective cohort: 271 patients (2021–2023)
• Categorized into:
  1. Never received blinatumomab
  2. Responded to blinatumomab
  3. Blinatumomab non-responders
• Key Results:
  • Overall response to CAR-T at Day 28: High (90%)
  • Long-term outcomes differ sharply:
    • Blinatumomab non-responders: 12-month progression-free survival 43%, overall survival 64%
    • Blinatumomab naive: 12-month PFS 72%, OS 86%
    • Blinatumomab responders: Outcomes similar to blinatumomab naive
  • “Patients who didn’t respond to blinatumab had higher risk disease features ... when we looked at longer term outcomes, patients who did not achieve a response to blinatumumab had worse post CAR T survival.” – Dr. Srinagesh [12:28]

Strengths and Limitations of Real World Data

• Real-world data critical for rare diseases due to sample size challenges
• Reflects true clinical practice; but comes with confounders and incomplete data
  • “Real world data also reflects real clinical practice and so ... whereas clinical trial populations may be selected and have limited generalizability.” – Dr. Srinagesh [14:56]

Mechanisms and Clinical Implications

• All patients retained CD19 expression
• “Really more work is required to understand the biological mechanisms at play.” – Dr. Srinagesh [16:00]
• Findings suggest blinatumomab non-responders might benefit from additional consolidative therapy (e.g., allogeneic transplant)
  • “We really need to understand the biology at play here—why patients who don’t respond to blinatumomab also tend not to respond to brexocel.” [17:00]
• Calls for stratification in future studies by blinatumomab response [18:23]

Clinical Takeaways

• CAR T therapy should not be withheld solely based on prior blinatumomab exposure
• Non-responders may need intensified follow-up and consolidation strategies
• Quote:
  • “Our data would indicate yes” (regarding stratifying future studies by blinatumomab response). – Dr. Srinagesh [18:23]

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Notable Quotes & Memorable Moments

• “The complexity means that earlier studies could only provide partial explanations. Our study addresses this gap...” – Dr. Lee [01:16]
• “If we can modulate this pathway, it may be possible to preserve polypoid megakaryocyte and improve platelet production.” – Dr. Lee [05:22]
• “We also know that high disease burden predicts inferior outcomes in both settings, but we don’t yet know the precise mechanism by which this happens.” – Dr. Srinagesh [16:00]
• “Blinatumomab non-responders are one such group that may benefit from a consolidative allo, but this needs to be studied in more detail.” – Dr. Srinagesh [17:00]

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Timestamps for Key Segments

• [00:38] — Start of ANKRD26 thrombocytopenia discussion (Dr. Lee)
• [04:10] — Key findings of the single cell study
• [05:16] — Therapeutic implications
• [08:06] — Future research directions for ANKRD26 work
• [09:55] — Start of CAR T/Blinatumomab discussion (Dr. Srinagesh)
• [12:28] — Main results and clinical significance
• [14:56] — Strengths and limitations of real-world data
• [16:00] — Mechanistic insights and need for future research
• [17:00] — How findings may inform future therapeutic decisions
• [18:23] — Recommendation for future study stratification

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Conclusion

This episode offers a comprehensive look at the molecular mechanisms underlying rare inherited thrombocytopenia and practical insights for sequencing immunotherapies in B-ALL. Both studies underscore the importance of high-resolution data and collaborative, real-world clinical research in advancing hematology practice.

For full articles and further reading, visit bloodjournal.org.

Transcript

[A]

Welcome to the American Society of Hematology Conversations with Blood Authors Podcast. This episode is hosted by Associate Editor Dr. Laurie Sen. She discusses single cell profiling of ANC RD 26 thrombocytopenia reveals progenitor expansion and polyploid apoptosis via Jun BP 21 with Dr. Shenguan Calvin Lee. She then talks with Dr. Hrishi Krishna Srinagesh regarding his article Blinitumum response correlates with poor survival after Brechsu Kabta Gene

[B]

hi, I'm Laurie Sen, Podcast Editor at Blood and Today I'm joined by Dr. Calvin Li from the Army Medical University in China. He's an author of the New Blood Journal article entitled Single cell profiling of ANCRD26 thrombocytopenia reveals progenitor expansion and and polypoid apoptosis via Jun B P21. Thanks for joining us today. Perhaps you can start by providing some background on how common angard26 thrombocytopenia is and its clinical manifestations.

[C]

The background about this disease is because it started with the NK26 late sample. Cytopenia is a very rare inherited platelet disorder caused by mutations in the regulatory regions of NKR26 gene. Patients typically have chronically low platelet counts and increased risk of bleeding. What makes this disease particularly difficult to study is the biology of macariotositis that the cells that produce platelet they are rare, fragile and highly heterogeneous. The complexity means that earlier studies could only provide partial explanations. Our study addresses this gap by creating a high resolution single cell atlas of mercaritocyte development across multiple patients.

[B]

What motivated you to study this specific entity and can you tell us more about your methodology?

[C]

The research beginning with very long standing clinical mystery patients with NCA 26 related frontopenia have low platelet counts, but the traditional models never fully explained why. We suspected that the real problem might not be visible at the bulk level. It might be hidden at the level of individual cells. With emergence of single cell transcriptomes, we finally had a tool capable of dissecting mekarytocyte development cell by cell. That allowed us to revisit the disease with much higher resolution and ask for a fundamental question where exactly does the platelet production fail and why? The goal for this research is to define the cellular and molecular mechanism behind platelet failure in the disease. Specifically, we wanted to map the four developmental trajectory of megakaryocyte, identify where the process diverges from normal, discover the molecular signals responsible for that failure. To do this, we Analyze the tens of thousands of individual cells from patients and the controls integrate single cell transcriptomes with the functional validation experiment.

[B]

And what were your key findings of this study?

[C]

We found two major abnormalities that consistently occurred across all patients. First, there was an expansion of megalitoside progenitors meaning that earlier precursor cells increased in number. Second, and more importantly, the maturectocytes failed to survive. The highly polypoid cells with normally generated platelets underwent premature apoptosis. Mechanistically, we discovered the overexpression of AKR 26 activate P21 pathway which drives the apoptosis in polypoid mackeretocytes independently of the classic p53 pathway. This provided first unified molecular expansions for platylase deficiency in this condition.

[B]

What do you think the potential therapeutic implications of these findings might be?

[C]

These findings have both mechanistic and clinical implications. Mechanistically they redefine the disease as a selective survival survival failure of mature mega keratocyte rather than simple a production problem. Clinically identified p21 pathway opens potential therapeutic opportunities. If we can modulate this pathway in it may be possible to preserve polypoid mega carotocyte and improve platelet production. More broadly. This work demonstrates how single cell technologies can resolve rare hematologic disease and that was previously too complex to decode.

[B]

Do you think that this mechanism might explain the increased risk of myeloid malignancies that's also seen in ancard 26 Thrombo cytopenia?

[C]

That's a really good question. Basically there's some exploitations out there and then if they look at it demagray. But I would think that because the complexity of this environment, perhaps the single cell technology will be able to map out this trajectory of the development and then figure out that molecular mechanism.

[B]

In his commentary, Dr. Thomas Pinchas from the St Justine Hospital in Canada recognizes the importance of the insights that your study has generated. But he also questions whether different genetic variants may result in alternate mechanisms of pathogenesis. Can you comment on this and the need to expand your study to include more patients?

[C]

That's because this dory is about these rare diseases. Actually 300 patient pedigrees worldwide. We realize that's the limitation in our research. Of course expanding the other category will be helpful. But again our research is basically about this offer of new methods which is a single cell transcriptome. But other research maybe use the same technology just mapping out the whole pathways and then we can figure that out the molecular cellular mechanisms out there. I think that's a good idea.

[B]

And finally moving forward, what are the next questions that you would like to see answered?

[C]

Moving forward, the next question we wanted to see is two things. One is the therapeutic target. So we need to figure out whether pharmacological maturation could stop this apoptosis and then enhance the platelet production and by figuring out moderate for this zone PV21 pathway. And then second of all, there's a lot of other in vivo study, particularly in the pathological condition in human in patients. We need to expand that area. It's the main to have some clinical trial to validate that.

[B]

I truly look forward to seeing the results of these next efforts. In the meantime, I hope you've enjoyed the conversation today with Calvin Lee who has discussed the newly published article Single cell profiling of ANCRD26 thrombocytopenia reveals progenitor expansion and polypoid apoptosis via Jun B P21. This study elucidates the pathophysiology of a rare heritable platelet disorder, revealing potential disease specific therapeutic targets. This article is now available on bloodjournal.org I'm also joined today by by Dr. Rishi Srinagesh from Stanford University. He's the lead author on a new Blood Journal article entitled Blinitumumab Non response Correlates with Poor survival after Brexitcaptogene. Thanks for joining us today.

[D]

Thank you Dr. San, and thank you to the Blood Editorial Board for featuring our article on your podcast and thanks to the listeners for tuning in.

[B]

Perhaps you can start today by providing some background on the current role of CAR T cell therapy in relapsed refractory all and the outcomes observed in clinical

[D]

trials, we now have multiple different immunotherapies including CAR T cells for relapsed refractory B all and many of these treatment approaches work in similar pathways by targeting CD19 on B cells. Brexacaptogene, autolucel or Brexocell is one such CD19 targeting car T cell that has demonstrated efficacy in the relapsed and refractory setting. But because we now have multiple immunotherapies that target the same antigen, there's emerging concern about using them in sequence. We know that several mechanisms of relapse are shared between CAR T cells and T cell engaging antibodies. These include CD19 downregulation and T cell exhaustion. And there's similar core prognostic markers for both treatment approaches like high disease burden. And so while Brexocell has been approved by the FDA for several years and induces responses in the majority of patients. There's concern about how to sequence immunotherapy in relapsed all.

[B]

Can you tell us about the ROCA Consortium and the motivation to do this study?

[D]

ROCA is the Real World Outcomes Collaborative for CAR T cells in adult all and it consists of 41 centers across the US that administer car T cells in the real world setting. ROCA has been studying outcomes of patients who receive brexocell for a number of years now, and while pivotal trials such as the Zuma 3 study have evaluated the role of prior blenatumab before brexocell on post car t outcomes, these studies were insufficiently powered to draw definitive conclusions about the outcomes of patients who receive one immunotherapy after the other. Leveraging this large unique data set, we sought to answer the question how does blenatumumab receipt in influence post brexisl outcomes?

[B]

Can you briefly describe your study methodology and the overall findings?

[D]

We conducted a large retrospective COHORT study including 271 patients who received BrexoCell in the Roca consortium between 2021 and 2023 and we analyzed patients with respect to three groups, those who had never received blenatumumab, those who responded to blenatumumab, and those who had not responded to blimitumumab. Overall, 59% of our cohort had received blimitumumab and about 2/3 of patients responded to blenatumumab 1/3 did not respond. Patients who didn't respond to blenatumab had higher risk disease features like pH, like disease status and higher disease burden at the time of apheresis. We also looked at post car t outcomes. Overall rates of safety events like cytokine release syndrome and neurotoxicity were similar across these three groups and across the cohort. Overall, initial responses at day 28 were high at 90%. However, when we looked at longer term outcomes, patients who did not achieve a response to blenatumumab had worse post CAR T survival. 12 month progression free survival amongst blenatumumab non responders was just 43% compared to 72% for patients who had never received blenitumumab and similarly, Overall survival at 12 months was significantly inferior 64% compared to 86% in the blenitumumab naive group. In contrast, the patients who received blenitumab but responded had similar post car t outcomes compared to the blenatumumab naive group.

[B]

That's quite A striking difference. What are some of the confounders that might be at play here and how did you control for those?

[D]

We constructed multivariable Cox models as well as inverse probability of treatment weighting models to adjust for potential confounders like prior therapies, including prior transplant disease burden. And even when we constructed these multivariable models, blenatumumab response status was still a significant predictor of post CAR T survival.

[B]

Can you comment on the strengths and the limitations of real world data sets in CAR T cell therapy research?

[D]

That's a really critical question. Many of our diseases for which we use CAR T cells are rare and so they require collaborative efforts across centers to generate sufficient numbers to draw meaningful insights, and ROCA aims to achieve just that. Real world data also reflects real clinical practice and so we can directly draw conclusions that apply to our patient populations, whereas clinical trial populations may be selected and have limited generalizability. On the other hand, non randomized data and real world data are challenging to interpret due to the presence of confounders and incomplete data, and so careful attention has to be applied to those issues to address potential study biases.

[B]

Based on this association that you've observed, do you think that this sheds any light on the underlying mechanism of immunotherapy resistance that's observed in these patients?

[D]

All the patients in our study who received Brexocell retained CD19 expression at the time of Afghanistan. However, I think a more detailed biological exploration of the mechanisms of resistance to sequential immunotherapy is really critical. We also know that high disease burden predicts inferior outcomes in both settings, but we don't yet know the precise mechanism by which this happens. And so I think we've identified a clear cohort of patients who have inferior outcomes after sequential immunotherapy. But really more work is required to understand the biological mechanisms at play.

[B]

In her commentary, Adele Fielding from the University of York states that this data will be of assistance to clinicians in planning and sequencing therapy and relapsed all. Can you comment on how your findings might inform treatment decisions moving forward?

[D]

First of all, I would like to highlight that overall patients who received blenatumumab had high response rates at day 28 to Brexocel, indicating the feasibility of using Brexocell even in blenatumumab exposed patients. So we don't think this CAR T therapy should be withheld from patients based only on belinutumumab receipt status. Second of all, even amongst non responders, given the high overall response rates. Brexocell is still a viable salvage option, but given the long term outcomes remain inferior amongst this group, they may benefit from additional consolidative therapy. A major unanswered question right now in adult B All cartel therapy is trying to understand which patients benefit from consolidated aloe transplant and I think blenatumumab non responders are one such group that may benefit from a consolidative aloe, but this needs to be studied in more detail. And second of all, we really need to understand the biology at play here why patients who don't respond to blinitumumab also tend not to respond to brexocell

[B]

in future studies, should patients be stratified based on prior blenatumab response?

[D]

Our data would indicate yes.

[B]

I'd like to thank you today for sharing the results of this important real world analysis and I look forward to future efforts of the ROCA Consortium. In the meantime, I hope you've enjoyed the conversation today with Richie Srinagesh, who has discussed the newly published article Blinitumumab Non response Correlates with Poor survival after Brexitcaptogene. This study highlights prior response to blenitumumab as a key predictor of response to CAR T cell therapy, which may inform therapeutic decision making in adult patients with relapsed B. All this article is now available on bloodjournal.org

[A]

thank you for listening to this episode of Conversations with Blood Authors. To read the articles, visit bloodjournal.org this episode is copyrighted by the American Society of Hematology.