Towards a CAR T-cell therapy approach for Calreticulin-mutated Myelofibrosis

骨髓纤维化（MF）是一种恶性骨髓疾病，由一群异常的克隆巨核细胞祖细胞驱动。它在英国的发病率为十万分之一，其特点是广泛的骨髓纤维化，导致血液生产效率低下，贫血，感染失控，出血，最终死亡。此外，10-20%的MF患者随后会发展为急性髓系白血病，这是一种紧急的、危及生命的疾病。目前，对MF没有满意的治疗方法。唯一有效的治疗方法是同种异体干细胞移植（allo-SCT），它只适用于年轻的、医学上适合的患者，但即使在这种情况下，它的结果也特别差。骨髓纤维化是一个被忽视的领域，医疗需求未得到满足。t细胞是一种特殊的免疫细胞，它的工作是寻找并杀死具有很强特异性的病毒感染细胞。通过在实验室中应用基因工程技术，现在有可能重新引导患者的t细胞识别并杀死他们的癌细胞，其效力与他们自然攻击病毒感染的效力相同。这是通过将一种称为嵌合抗原受体（CAR）的人工蛋白质插入患者的t细胞中来产生CAR - t细胞来实现的。CAR - t细胞代表一种“活的药物”，形成患者免疫系统的一部分，防止复发。CAR - t细胞对传统疗法无效的血癌非常有效：在对b细胞白血病患者的研究中，可以观察到90%以上的病例对CAR - t细胞疗法完全有效，50%以上的儿童/青年白血病患者通过单剂量治疗被“治愈”。本项目的重点是开发用于MF的CAR - t细胞，将突变的细胞表面蛋白mutCALR（突变钙网蛋白）靶向于恶性细胞。在所有MF病例中有25%发现mutCALR，它是CAR - t细胞的一个极好的潜在靶标。我们的方法将是利用已知的实验室技术开发一种靶向mutCALR的抗体，并将这种抗体设计成CAR格式。然后，我们将继续在一系列体外和体内环境中测试mutCALR CAR，以确定它作为未来MF治疗方法的有效性和安全性。我们相信CAR-T疗法对骨髓纤维化患者来说是一个很好的治疗选择。这种疾病的慢性性质意味着有充足的时间来制造个性化的CAR-T细胞，这是其他恶性肿瘤快速发展的一个主要问题。此外，似乎在25%的病例中，疾病是由恶性细胞表面的mutCALR驱动的，因此使用CAR-T细胞的靶向免疫治疗可以完全消除疾病，同时提供持久的肿瘤免疫。

Myelofibrosis (MF) is a malignant bone marrow disease, driven by a population of abnormal, clonal megakaryocyte progenitor cells. It has an incidence of 1 in 100,000 in the UK and is characterised by extensive bone marrow fibrosis which leads to ineffective blood production, anaemia, uncontrolled infection, bleeding and ultimately death. Further, 10-20% of MF patients will subsequently develop Acute Myeloid Leukaemia which is an urgent, life-threatening condition. Currently, there are no satisfactory treatments for MF. The only curative therapeutic approach is an allogeneic stem cell transplant (allo-SCT), which is only suitable for younger, medically fit patients, but even in this setting, it has a particularly poor outcome. Myelofibrosis is a neglected area with unmet medical need. A T-cell is a specialised immune cell whose job is to seek out and kill virus infected cells with great specificity. By applying gene engineering techniques in the laboratory, it is now possible to redirect patient T-cells to recognise and kill their cancer cells with the same potency as they would naturally attack a viral infection. This is done using by inserting an artificial protein called a chimeric antigen receptor (CAR) into patient T-cells to create CAR T-cells. CAR T-cells represent a 'living drug', forming part of the patient's immune system, preventing recurrence. CAR T-cells are highly effective against blood cancers that do not respond to conventional therapies: in studies of patients with B-cell leukaemia, complete responses to CAR T-cell therapy can be observed in over 90% of cases and over 50% of children/young adults with leukaemia are 'cured' by a single dose.The focus of this project is to develop CAR T-cells for MF, targeting the mutated cell surface protein mutCALR (mutated Calreticulin) on the malignant cells. mutCALR is found in 25% of all cases of MF and represents an excellent potential target for CAR T-cells. Our approach will be to develop an antibody targeting mutCALR using known laboratory techniques and to engineer this antibody into CAR format. We will then proceed to test the mutCALR CAR in a series of in vitro and in vivo settings to define how effective and safe it may be as a future therapy for MF.We believe that CAR-T therapy can be a very good treatment option for patients with Myelofibrosis. The chronic nature of the disease means that there is ample time to manufacture personalised CAR-T cells which is a main problem in other malignancies that progress quickly. Additionally, it appears that in 25% of cases, the disease is driven by mutCALR on the surface of the malignant cells, such that targeted immunotherapy using CAR-T cells may eliminate the disease completely, whilst providing lasting tumour immunity.