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前言在过去的几十年中，对DNA损伤反应（DDR）途径的理解不断加深，拓宽了肿瘤学的治疗领域。越来越清楚的是，DNA损伤反应缺陷导致的细胞基因组不稳定性导致了癌症的发生。另一方面，这些缺陷也可以作为一个治疗机会。越来越多的DDR靶向药物已迅速扩展到参与DDR途径的多个成员的抑制剂，包括PARP、ATM、ATR、CHK1、WEE1和DNA-PK。目前，这些DDR成分的抑制剂，其中一些正处于临床研究中。此外，新的证据表明DDR抑制剂对传统癌症治疗的敏感性，以及DDR途径和免疫检查点抑制剂（ICI）反应之间的相关性，这些都促进基于DDR抑制剂的联合治疗。靶向DNA修复途径的药物正在肿瘤治疗领域显示出越来越大的作用。DNA损伤与DNA损伤反应为了保持基因组的完整性，复杂的DNA修复系统被用来对抗各种形式的DNA损伤，这些机制被称为DNA损伤反应。DDR通路分为三个功能上相互交织的部分：检测DNA损伤的传感器、触发信号级联的信号转换器和阻碍DNA修复的效应器。这些途径不是相互排斥的过程，而是相互协调，形成DNA修复的精确调控网络。             碱基切除修复（BER）和核苷酸切除修复（NER）所有生物体的基因组都在不断地经历微妙的变化，这是由于内源性产生的各种基因毒物，如活性氧（ROS）、电离辐射以及烷基化剂等环境损伤所致。DNA中的大多数细微变化，如单链断裂（SSB），都是通过BER途径修复的。BER首先由受损的碱基启动，然后切除碱基并用新合成的DNA替换。然后，脱嘌呤/脱嘧啶核酸内切酶（APE）切割AP位点，在损伤位点形成3′OH末端。最后，DNA聚合酶和DNA连接酶在去除损伤碱基产生的核苷酸缺口处被招募，从而封闭缺口。BER负责修复小损伤，而使DNA螺旋结构变形的较大的双链断裂（DSB）则需要NER途径修复。NER机制涉及一种关键蛋白质，即切除修复交叉互补蛋白1（ERCC1），它会清除断裂点附近的DNA，然后用正常的DNA复制进行替换。同源重组（HR）和非同源末端连接（NHEJ）在哺乳动物细胞中，HR和NHEJ是修复DSB的两条主要途径。由于同源姐妹染色单体是新DNA合成所需的模板，HR途径可以在S/G2细胞周期阶段修复DSB，而NHEJ在除M期外的所有细胞周期阶段都是活跃的。HR分析来自基因组其他部分的同源序列，收集断裂位点丢失的信息。HR首先切除断裂端，随后通过Brca2和Rad51形成Rad51核蛋白丝，开始检索同源序列，并促进断裂DNA和同源模板之间形成连接分子，完成修复。NHEJ比HR更简单一些，直接将断裂端重新连接在一起。NHEJ所需的基本因子是由Ku70/Ku80和DNA依赖性蛋白激酶的催化亚单位（DNA-PKcs）组成的异二聚体，其识别DSB并促进NHEJ的下游信号因子，如XRCC4、XLF和DNA连接酶IV。虽然NHEJ机制较为简单，但有时会导致重排，而HR被认为不会产生错误。除HR和NHEJ外，一种DSB修复途径与这两个主要DSB修复途径具有相似的机制，但在遗传上不同，称为替代末端连接（a-EJ）途径。a-EJ途径既可以与HR共享类似的起始过程，也可以与NHEJ一样组成无同源模板的DNA末端连接因子。目前，越来越多的研究开始关注a-EJ通路作为NHEJ或HR活性受损癌细胞的潜在治疗靶点。错配修复（MMR）除了暴露于基因毒素的细胞所产生的损伤外，DNA损伤也可能来自异常的DNA处理。针对复制相关错误的DNA修复途径称为MMR。在DNA合成过程中，MMR纠正核苷酸错误整合，从而防止分裂细胞中永久性的DNA改变。因此，基因突变或表观遗传沉默导致的MMR缺陷可能导致自发突变的发生率增加，这通常与遗传性和散发性癌症有关。跨损伤合成与模板置换DNA损伤耐受性（DDT）作为修复复制停滞DNA损伤的一种基本旁路机制，允许DNA复制穿过阻碍元件。跨损伤合成（TLS）是两种不同的DDT模式之一，取决于一种特殊的TLS聚合酶的功能，而不是复制性DNA聚合酶，其可以直接跨过损伤部位复制。由于TLS聚合酶的校对活性不足，TLS机制是容易出错的，这增加了突变的风险。毫不奇怪，TLS是细胞突变的主要来源。相反，DDT的另一种模式，即模板置换（TS），涉及在姐妹染色单体上重组到同源DNA模板，这类似于HR过程，被认为比TLS更准确。TLS和TS的修复活动开始于复制叉之后，这表明它们可能发生在DNA复制期间或之后，TS开始于S期早期，TLS开始于S期晚期。范可尼贫血（FA）途径范可尼贫血是一种罕见的遗传病，由范可尼基因的双等位基因突变引起，受影响的患者伴有对DNA损伤的反应不足。范科尼贫血已被确定为一种DNA修复途径，可清除阻碍DNA复制和转录的屏障，即DNA链间交联（ICL）。ICL可由醛类在多种代谢反应（如脂质过氧化和乙醇代谢）和化疗（如铂）期间形成。而链内交联通过NER途径修复，而ICL主要通过FA途径修复。通过UHRF1蛋白和FANCM–MHF1–MHF2复合物检测ICL后，FA核心复合物被招募到染色质中，并单泛素化底物FANCI和FANCD2。泛素化FANCD2-I为各种DNA内切酶招募支架蛋白，从而完成对交联处DNA的识别和核苷酸的切除，从而得到适合重组修复的DNA底物。O6-甲基鸟嘌呤-DNA甲基转移酶途径众所周知，DNA甲基化剂能够抑制DNA甲基化并产生广泛的DNA加合物，如O6-甲基鸟嘌呤（O6MeG）和O4-甲基胸腺嘧啶，这可能导致碱基错配和随后的点突变。其中，O6MeG被认为是甲基化剂诱导的DNA加合物的主要来源，可导致突变和致癌。O6MeG可以通过O6-甲基鸟嘌呤-DNA甲基转移酶（也称为MGMT）在单步自杀反应中修复。MGMT将受损鸟嘌呤O6位点的甲基转移到半胱氨酸残基，从而防止基因突变。可以想象，MGMT降低了烷化剂在癌细胞中的作用，可能导致化疗耐药。MGMT启动子的甲基化会阻碍其转录，因此可以用来提高细胞对烷化剂的敏感性。DDR治疗应用的机制与正常细胞相比，肿瘤细胞对DNA损伤敏感性增加的潜在机制在于三个主要方面：至少一条DDR途径的缺陷、复制应激的升高和内源性DNA损伤的增加。DDR缺陷尽管DDR缺陷与癌症的发生和发展有关，但DDR途径中的缺陷也为靶向肿瘤细胞提供了治疗机会。携带DDR缺陷的肿瘤细胞导致基因组不稳定性增强，并依赖剩余的DDR途径生存。作为一种治疗方法，剩余DNA修复途径的组合靶向产生了一种被称为“合成致死”的概念。合成致死的概念基于两个同时发生的功能丧失遗传事件，其中任何一个单独都不会导致损伤，而是共同作用导致细胞死亡。当癌细胞特有的DDR途径发生一种基因改变时，由DDR抑制剂引起的第二种功能丧失事件将在不影响正常细胞的情况下对癌细胞合成致死。复制应激真核细胞复杂的DNA复制系统在细胞分裂过程中受到细胞周期中各种蛋白质的严格调控。许多DNA核苷酸需要精确聚合以确保细胞内稳态。阻碍或终止复制叉进展的内源性或外源性障碍激活保守的细胞反应途径，称为复制应激。复制应激的分子机制是DNA聚合酶的进展停滞和随后DNA聚合与DNA解旋酶的解偶联。诱导复制应激的一个例子是G1/S细胞周期检查点缺陷，其原因可能是pRb功能丧失、CDKN2A缺失或细胞周期蛋白D1或细胞周期蛋白E扩增。 内源性DNA损伤一些内源性性DNA损伤是中性pH条件下低浓度氢离子和氢氧根离子的作用造成的，如脱嘌呤和脱嘧啶作用。细胞内环境对于染色体DNA来说，还具有其他危险，其中最严重的来自氧化过程，在线粒体产生的一些中间产物，如ROS，可能会从线粒体渗出，进入细胞质。这样的中间产物包括超氧离子、过氧化氢和羟自由基。在肿瘤代谢中，低PH值、缺氧和高水平的ROS在肿瘤微环境（TME）中普遍存在。靶向DNA修复途径的抑制剂目前利用DDR缺陷的抗癌策略在很大程度上是通过开发抑制DNA修复过程中分子的靶向药物来解决的。聚ADP-核糖聚合酶（PARP）抑制剂PARP抑制剂的发展是合成致死的典型代表。PARP1和PARP2是关键的DDR酶，通过带负电荷的聚ADP-核糖（PAR）链修饰靶蛋白，感知DNA损伤并传递信号。PARP1与受损DNA结合后的结构变化激活其催化功能，促进DNA修复效应分子的招募和DNA损伤部位周围染色质的结构重塑，而染色质的动态重塑将在很大程度上影响DNA修复的效率。                        鉴于PARP在促进DNA有效修复中的关键作用，PARP抑制剂可以选择性地杀死同源重组缺陷的肿瘤细胞。PARP抑制剂是BRCA突变肿瘤的一种很有前途的治疗策略。聚ADP-核糖水解酶（PARG）抑制剂PARG通过在DNA损伤后水解PAR核糖键来逆转PARP酶的作用。同样，PARG在DNA复制和修复中的积极作用导致PARG缺陷细胞对DNA损伤剂的敏感性增加。尽管大量研究表明PARP抑制剂与合成致死率之间存在相关性，但对PARG抑制剂治疗机制的研究却相对滞后。据报道，乳腺癌细胞中HR蛋白（如BRCA1/2）的缺失可刺激PARG抑制细胞的合成致死性，PARG抑制剂COH34可诱导BRCA突变或对奥拉帕利耐药的卵巢癌和乳腺癌细胞死亡。然而，在其他癌细胞中报告了相互矛盾的结果。在六个测试的乳腺癌细胞系中，只有一个BRCA缺陷的细胞系对PARG抑制剂PDD00017273敏感，而五个细胞系对PDD00017273（包括BRCA突变的细胞系）无效。共济失调毛细血管扩张突变蛋白（ATM）抑制剂DDR信号级联由一系列蛋白磷酸化驱动，ATM、ATR和DNA-PKs是参与该过程的关键激酶。被DNA双链断裂激活，ATM被MRE11-RAD50-NBS1（MRN）复合物招募到DSB位点。ATM底物包括p53、CHK1和CHK2，它们的磷酸化将导致S内或G2/M细胞周期阻滞。尽管ATM在DNA修复等多种分子过程中起着典型作用，但它也具有非典型功能，包括剪接体置换。ATM被认为是肿瘤抑制因子，ATM缺陷或突变在实体瘤和B细胞淋巴瘤中比较常见。ATM突变可能导致共济失调毛细血管扩张症，这是一种神经退行性疾病，其容易导致癌症。目前有几种ATM抑制剂正在研究用于癌症治疗。共济失调毛细血管扩张症和Rad3相关蛋白（ATR）抑制剂与由DSB触发的ATM不同，ATR被复制蛋白A（RPA）包裹的单链DNA激活并被招募。单链DNA可以通过DSB的核溶解处理以及复制DNA解旋酶与DNA聚合酶的解偶联产生。细胞内ATR信号涉及一系列下游分子的磷酸化，触发广泛的反应，包括阻断细胞周期检查点、DDR和细胞凋亡。与其他DDR蛋白如PARP相比，ATR抑制剂的开发相对滞后。原因可能包括ATR分子的大尺寸和对其晶体结构缺乏了解。此外，其在所有PIKK中的高度同源活性位点以及对共激活蛋白的需求进一步限制了其药物设计。CHK1抑制剂检查点激酶CHK1通过磷酸化和招募一系列调节蛋白，积极参与ATR和ATM启动的DNA损伤反应。CHK1通过磷酸化CDC25A来调节S期内检查点，导致CDC25A降解，随后S期细胞周期蛋白依赖性激酶2（CDK2）活性降低，CHK1对CDC25C和WEE1的磷酸化调节有丝分裂和G2/M检查点。此外，CHK1还磷酸化Thr-309上的RAD51，促进其在HR期间与BRCA2的相互作用。CHK1水平升高与更差的预后、疾病复发和治疗抵抗相关，这进一步支持CHK1抑制的治疗潜力。WEE1抑制剂作为对DNA损伤的反应，激活的ATR使Chk1磷酸化，Chk1又使WEE1和CDC25磷酸化。与活性被磷酸化抑制的CDC25相比，WEE1被激活，然后磷酸化下游CDK1上的Tyr15和Thr14以抑制其活性，导致G2/M周期阻滞，为DNA损伤修复留出时间。此外，通过磷酸化CDK1上的Tyr15，WEE1还可以在DNA复制完成之前阻止S期向G2期的进展。虽然WEE1抑制剂的原理是明确的，但其临床应用受到其治疗窗口的限制。目前，大多数临床研究集中于WEE1抑制与化疗药物的联合应用。DNA-PK抑制剂DNA依赖性蛋白激酶是一个由DNA激活的丝氨酸/苏氨酸蛋白激酶，大量表达在几乎所有哺乳动物的细胞中。DNA-PK是DNA修复的关键蛋白激酶， 参与了NHEJ的过程 。在各种肿瘤类型（包括胃肠道癌、肺癌和肝细胞癌）中都观察到DNA-PK表达上调，并且与较高的肿瘤分级和不良预后相关。DNA-PK抑制剂的开发主要集中在DNA-PKcs的催化活性上，而新的抗DNA-PKcs方法，如DNA-PKcs抑制性microRNA或靶向Ku异二聚体的抑制剂，则基于ATP结合位点的同源模型。目前，大多数DNA-PK抑制剂的临床研究集中在与癌症化疗或放疗联合使用的效果。小结细胞对DNA损伤的反应是一个复杂的过程，涉及各种信号网络和蛋白质，它们在特定的癌症类型中被差异激活或失活。肿瘤中增加的复制应激和DNA修复缺陷为我们治疗癌症提供了机会，使得癌细胞比正常细胞更容易受到DDR抑制。目前，以PARP抑制剂为典型的靶向DDR途径的药物已经走向临床应用，并且在肿瘤治疗中展现出令人鼓舞的前景。进一步，确定这些DDR抑制剂的最佳剂量、组合和时间表，减少不良反应，更理想地提高疗效将是未来的方向。此外，对每一种肿瘤进行表征，以确定其失控的DDR成分的具体特征，将有助于癌症患者的个性化治疗。参考文献：1.  Targeting DNA repair pathway in cancer:Mechanisms and clinical application. MedComm (2020). 2021 Dec; 2(4):654–691.声明：发表/转载本文仅仅是出于传播信息的需要，并不意味着代表本公众号观点或证实其内容的真实性。据此内容作出的任何判断，后果自负。若有侵权，告知必删！长按关注本公众号   粉丝群/投稿/授权/广告等请联系公众号助手 觉得本文好看，请点这里↓

SBT-589 showed mitochondrial protection across models of Friedreich's ataxia SBT-589 displayed cardioprotective effects in aggressive mouse model of FA cardiomyopathy Ongoing studies are expected to build on these insights as SBT-589 progresses through developmental stage-gates NEEDHAM, Mass., March 19, 2024 /PRNewswire/ -- Stealth BioTherapeutics Inc. (the "Company" or "Stealth"), a clinical-stage biotechnology company focused on the discovery, development, and commercialization of novel therapies for diseases involving mitochondrial dysfunction, announced today the presentation of new SBT-589 data demonstrating cardioprotective effects across pre-clinical models of Friedreich's ataxia (FA). The data were presented at the Wellcome Trust Conference on Mitochondrial Medicine – Therapeutic Development, held March 18-20, 2024, in Cambridge, England. FA is a chronic disease of metabolic disruption that is typically diagnosed in childhood or adolescence, is inexorably progressive and usually results in premature death from cardiomyopathy or heart failure. There are no approved therapies for the progressive cardiomyopathy, which is linked to severe mitochondrial dysfunction, and is the leading cause of early death in this devastating disease. SBT-589 is a promising novel molecule that acts on mitochondrial pathways essential for cellular health and energy production that are impaired in FA cardiomyopathy. To evaluate the potential of SBT-589 in FA, a series of studies were conducted in FA patient-derived cells, isolated heart mitochondria, and an aggressive mouse model of FA cardiomyopathy. SBT-589 improved bioenergetics in FA patient-derived cells and mitochondria. In an FA mouse model with prominent cardiac hypertrophy and aggressive mortality, mice treated with once-daily SBT-589 displayed significantly reduced cardiac hypertrophy and a delay in the onset of mortality compared to vehicle-treated mice. "Mitochondrial dysfunction is a central contributor to pathology in Friedreich's ataxia, a disease in which heart failure and sudden cardiac events are among the leading causes of mortality," said David A. Brown, Senior Vice President, Discovery. "Mitigating heart disease in FA is central to Stealth's ongoing efforts to improve the lives of individuals with FA. The new findings presented today support continued development of SBT-589 as a potentially disease-modifying therapy to address the unmet need in cardiomyopathy associated with Friedreich's ataxia." The data were presented by Dr. Laura E. Kropp, Senior Manager of Discovery Biology at Stealth, and recipient of the Keith Michael Andrus Cardiac Award from the Friedreich's Ataxia Research Alliance. About Friedreich's Ataxia Friedreich's ataxia is a rare genetic disease affecting an estimated 1 in 50,000 individuals in the United States. The disease is caused by a defect in the frataxin gene resulting in a relative deficiency of frataxin, leading to mitochondrial iron accumulation and oxidative stress. More than 90% of patients with Friedreich's ataxia experience progressive cardiomyopathy which usually becomes fatal by early adulthood and is the leading cause of early mortality. About Stealth BioTherapeutics Stealth BioTherapeutics is a clinical-stage biotechnology company focused on the discovery, development, and commercialization of novel therapies for age-related and rare genetic diseases involving mitochondrial dysfunction. The Company is initiating Phase 3 clinical trials of elamipretide, its lead investigational product candidate, in dry age-related macular degeneration. Elamipretide is also being tested in a fully enrolled Phase 3 clinical trial in primary mitochondrial myopathy, a rare skeletal myopathic disease caused by nuclear DNA mutations, and is the subject of a New Drug Application for Barth syndrome, an ultra-rare cardioskeletal disease. The Company is evaluating its second-generation clinical-stage candidate, SBT-272, for ophthalmic and neurological disease indications. The Company has a deep pipeline of novel mitochondria-targeted compounds under evaluation as therapeutic product candidates. Several of these lead compounds, including SBT-589, have progressed through pre-clinical development stage-gates and toward IND-enabling studies. Investor Contact Kendall Investor Relations Adam Bero, Ph.D. [email protected] [email protected] Media Contact Anna Stallman Communications Anna Stallman [email protected] SOURCE Stealth BioTherapeutics Inc.

Positive top-line data from Phase 2 dose exploration study of nomlabofusp, which was generally well-tolerated, with dose-dependent increases in tissue frataxin levels observedInitiated discussions with the Food and Drug Administration (FDA) on the potential use of tissue frataxin levels as a novel surrogate endpoint to support a Biologics License Application (“BLA”) submission for accelerated approval targeted for 2H 2025In January 2024, initiated open label extension (OLE) study with 25 mg daily dosing of nomlabofusp, with first patient dosed in March 2024; interim data expected in Q4 2024 Recent successful financing that raised $161.6 million extends expected operating runway into 2026. BALA CYNWYD, Pa., March 14, 2024 (GLOBE NEWSWIRE) -- Larimar Therapeutics, Inc. (“Larimar”) (Nasdaq: LRMR), a clinical-stage biotechnology company focused on developing treatments for complex rare diseases, today reported its fourth quarter and full year 2023 operating and financial results. “This year we made tremendous progress across key clinical and regulatory milestones for our nomlabofusp program. We were thrilled to recently report positive top-line data and successful completion of our Phase 2 dose exploration study. Nomlabofusp was generally well-tolerated and demonstrated dose-dependent increases in skin and buccal cell frataxin levels. Importantly, skin frataxin levels as a percentage of levels in healthy volunteers more than doubled in all patients after 14 days of daily treatment with 50 mg. The clear dose-response and the magnitude of increase in tissue frataxin levels further reinforces the therapeutic potential of nomlabofusp to address frataxin deficiency, the known root cause of disease in patients with Friedreich’s ataxia (FA),” said Carole Ben-Maimon, MD, President, and Chief Executive Officer of Larimar. “Additionally, the first patient in our OLE study has been dosed. The OLE study will inform on the long-term safety profile and long-term tissue frataxin levels. We remain on track to report interim data from the OLE study in the fourth quarter of 2024.” Dr. Ben-Maimon continued, “On the regulatory front, we are continuing discussions with the FDA on the potential use of frataxin as a novel surrogate endpoint to support accelerated approval. We are also beginning to plan for a global double-blind placebo-controlled confirmatory study expected to be initiated prior to a potential BLA submission. The BLA submission is targeted for the second half of 2025. We believe our clinical datasets supporting nomlabofusp’s differentiated mechanism of action, coupled with our strengthened balance sheet and expected runway into 2026, strongly position us for execution of our upcoming pivotal milestones designed to help address the urgent unmet needs of the FA community.” Recent Highlights In February 2024, Larimar announced positive top-line data and successful completion of its four-week, placebo-controlled Phase 2 dose exploration study of nomlabofusp (CTI-1601) in patients with FA. Nomlabofusp was generally well-tolerated up to 4-weeks, had a predictable pharmacokinetic profile, and led to dose-dependent increases in frataxin in skin and buccal cells after daily dosing of 14 days followed by every other day dosing until day 28 in the 25 mg and 50 mg cohorts. Increases in frataxin levels in skin cells were seen in all treated patients, and in buccal cells for the majority of patients. At Day 14, all patients (with quantifiable levels at baseline and Day 14) treated with 50 mg of nomlabofusp achieved frataxin levels in skin cells greater than 33% of the average level found in healthy volunteers, with 3 patients achieving levels greater than 50% of the average healthy volunteer level.In February 2024, Larimar announced that it had initiated discussions with the FDA on use of tissue frataxin levels as a potential novel surrogate endpoint. Larimar received FDA acknowledgement that frataxin deficiency appears to be critical to the pathogenic mechanism of FA, and that there continues to be an unmet need for treatments that address the underlying disease pathophysiology. Discussions to support an accelerated approval are ongoing with a BLA submission targeted for 2H 2025.In February 2024, Larimar raised net proceeds of approximately $161.6 million through a public offering of common stock. In March 2024, the first patient in the OLE study evaluating daily subcutaneous injections of 25 mg of nomlabofusp self-administered or administered by a caregiver was dosed. Participants who completed treatment in the Phase 2 dose exploration trial, or who previously completed a prior clinical trial of nomlabofusp, are potentially eligible to screen for the OLE study. The OLE study will evaluate the safety and tolerability, pharmacokinetics, and frataxin levels in peripheral tissues as well as other exploratory pharmacodynamic markers (lipid profiles and gene expression data) following long-term subcutaneous administration of nomlabofusp. Clinical assessments collected during the trial will be compared to data from a matched control arm derived from participants in the Friedreich’s Ataxia Clinical Outcome Measures Study (FACOMS) database. Interim data is expected in Q4 2024. To potentially escalate dose in the OLE study, data from the 50 mg cohort of the Phase 2 study, as well as available data from the 25 mg dose in the OLE study will be submitted for FDA review due to continued partial clinical hold. Fourth Quarter and Full Year 2023 Financial Results As of December 31, 2023, the Company had cash, cash equivalents and marketable securities totaling $86.8 million. As noted above, in February 2024, we raised approximately $161.6 million in net proceeds through a public offering of common stock. The Company reported a net loss for the fourth quarter of 2023 of $13.0 million, or $0.30 per share, compared to a net loss of $9.4 million, or $0.21 per share, for the fourth quarter of 2022. Research and development expenses for the fourth quarter of 2023 were $10.6 million compared to $7.2 million for the fourth quarter of 2022. The increase in research and development expenses compared to the prior year period was primarily driven by an increase of $1.1 million in drug manufacturing costs, an increase of $0.8 million in consulting expenditures, an increase of $0.7 million in personnel expense, an increase of $0.4 million in clinical costs related to an increase in the OLE study partially offset by a decrease in clinical costs associated with the Phase 2 nomlabofusp trial discussed above. General and administrative expenses for the fourth quarter of 2023 were $3.5 million compared to $3.2 million for the fourth quarter of 2022. The increase in general and administrative expense was primarily driven by an increase of $0.2 million in stock-based compensation expense associated with stock option grants made in 2023, an increase of $0.1 million in personnel expense and an increase of $0.1 million in operational costs primarily related to technology, partially offset by a decrease of $0.2 million in legal fees. For the full year 2023, the Company reported a net loss of $36.9 million, or $0.84 per share, compared to a net loss of $35.4 million, or $1.37 per share for the same period in 2022. Research and development expenses for the full year 2023 were $27.7 million compared to $24.3 million for the same period in 2022. The increase in research and development expenses compared to the prior year period was primarily driven by an increase of $1.9 million in personnel expense, an increase of $1.3 million in clinical expense, an increase of $1.1 million in consulting expenditures, an increase of $0.5 million in nonclinical development costs, an increase of $0.5 million in internal lab costs, and an increase of $0.3 million in stock-based compensation expense associated with stock option grants made in 2022 and 2023, partially offset by a decrease of $2.0 million in drug manufacturing costs and a decrease of $0.2 million in royalty fees associated with the milestone achieved in 2022. General and administrative expenses for the full year 2023 were $14.1 million compared to $12.3 million for the same period in 2022. The increase in general and administrative expense was primarily driven by an increase of $0.7 million in stock-based compensation expense associated with stock option grants made in 2022 and 2023, an increase of $0.5 million in personnel expense, an increase of $0.5 million in operational costs primarily related to technology and an increase of $0.4 million in professional fees primarily related to legal, accounting and consulting services, partially offset by a decrease of $0.3 million in insurance expense. About Larimar TherapeuticsLarimar Therapeutics, Inc. (Nasdaq: LRMR), is a clinical-stage biotechnology company focused on developing treatments for complex rare diseases. Larimar’s lead compound, nomlabofusp, is being developed as a potential treatment for Friedreich's ataxia. Larimar also plans to use its intracellular delivery platform to design other fusion proteins to target additional rare diseases characterized by deficiencies in intracellular bioactive compounds. For more information, please visit: https://larimartx.com. Forward-Looking StatementsThis press release contains forward-looking statements that are based on Larimar’s management’s beliefs and assumptions and on information currently available to management. All statements contained in this release other than statements of historical fact are forward-looking statements, including but not limited to statements regarding Larimar’s ability to develop and commercialize nomlabofusp (also known as CTI-1601) and other planned product candidates, Larimar’s planned research and development efforts, including the timing of its nomlabofusp clinical trials, interactions with the FDA and overall development plan and other matters regarding Larimar’s business strategies, ability to raise capital, use of capital, results of operations and financial position, and plans and objectives for future operations. In some cases, you can identify forward-looking statements by the words “may,” “will,” “could,” “would,” “should,” “expect,” “intend,” “plan,” “anticipate,” “believe,” “estimate,” “predict,” “project,” “potential,” “continue,” “ongoing” or the negative of these terms or other comparable terminology, although not all forward-looking statements contain these words. These statements involve risks, uncertainties and other factors that may cause actual results, performance, or achievements to be materially different from the information expressed or implied by these forward-looking statements. These risks, uncertainties and other factors include, among others, the success, cost and timing of Larimar’s product development activities, nonclinical studies and clinical trials, including nomlabofusp clinical milestones and continued interactions with the FDA; that preliminary clinical trial results may differ from final clinical trial results, that earlier non-clinical and clinical data and testing of nomlabofusp may not be predictive of the results or success of later clinical trials, and assessments; that the FDA may not ultimately agree with Larimar’s nomlabofusp development strategy; the potential impact of public health crises on Larimar’s future clinical trials, manufacturing, regulatory, nonclinical study timelines and operations, and general economic conditions; Larimar’s ability and the ability of third-party manufacturers Larimar engages, to optimize and scale nomlabofusp’s manufacturing process; Larimar’s ability to obtain regulatory approvals for nomlabofusp and future product candidates; Larimar’s ability to develop sales and marketing capabilities, whether alone or with potential future collaborators, and to successfully commercialize any approved product candidates; Larimar’s ability to raise the necessary capital to conduct its product development activities; and other risks described in the filings made by Larimar with the Securities and Exchange Commission (SEC), including but not limited to Larimar’s periodic reports, including the annual report on Form 10-K, quarterly reports on Form 10-Q and current reports on Form 8-K, filed with or furnished to the SEC and available at www.sec.gov. These forward-looking statements are based on a combination of facts and factors currently known by Larimar and its projections of the future, about which it cannot be certain. As a result, the forward-looking statements may not prove to be accurate. The forward-looking statements in this press release represent Larimar’s management’s views only as of the date hereof. Larimar undertakes no obligation to update any forward-looking statements for any reason, except as required by law. Investor Contact: Joyce Allaire LifeSci Advisors jallaire@lifesciadvisors.com (212) 915-2569 Company Contact:Michael Celano Chief Financial Officermcelano@larimartx.com(484) 414-2715 Larimar Therapeutics, Inc.Consolidated Balance Sheet(dollars in thousands except share and per share data) December 31, December 31, 2023 2022 Assets Current assets: Cash and cash equivalents $26,749 $26,825 Marketable securities 60,041 91,603 Prepaid expenses and other current assets 3,385 2,311 Total current assets 90,175 120,739 Property and equipment, net 684 831 Operating lease right-of-use assets 3,078 2,858 Restricted cash 1,339 1,339 Other assets 659 638 Total assets $95,935 $126,405 Liabilities and Stockholders’ Equity Current liabilities: Accounts payable $1,283 $1,686 Accrued expenses 7,386 8,408 Operating lease liabilities, current 837 611 Total current liabilities 9,506 10,705 Operating lease liabilities 4,709 4,797 Total liabilities 14,215 15,502 Commitments and contingencies (See Note 8) Stockholders’ equity: Preferred stock; $0.001 par value per share; 5,000,000 shares authorized as of December 31, 2023 and December 31, 2022; no shares issued and outstanding as of December 31, 2023 and December 31, 2022 — — Common stock, $0.001 par value per share; 115,000,000 shares authorized as of December 31, 2023 and December 31, 2022; 43,909,069 and 43,269,200 shares issued and outstanding as of December 31, 2023 and December 31, 2022, respectively 43 43 Additional paid-in capital 270,150 262,496 Accumulated deficit (188,554) (151,605) Accumulated other comprehensive loss 81 (31) Total stockholders’ equity 81,720 110,903 Total liabilities and stockholders’ equity $95,935 $126,405 Larimar Therapeutics, Inc.Consolidated Statements of Operations(In thousands, except share and per share data) Three Months Ended December 31, Year Ended December 31, 2023 2022 2023 2022 Operating expenses: Research and development $10,648 $7,218 $27,670 $24,250 General and administrative 3,514 3,221 14,088 12,276 Total operating expenses 14,162 10,439 41,758 36,526 Loss from operations (14,162) (10,439) (41,758) (36,526)Other income, net 1,169 1,014 4,809 1,171 Net loss $(12,993) $(9,425) $(36,949) $(35,355)Net loss per share, basic and diluted $(0.30) $(0.21) $(0.84) $(1.37)Weighted average common shares outstanding, basic and diluted 43,905,903 43,897,603 43,901,241 25,761,394