Immunologic Profiling of Immune-Related Cutaneous Adverse Events with Checkpoint Inhibitors Reveals Polarized Actionable Pathways.

PURPOSE: Immune-related cutaneous adverse events (ircAE) occur in ≥50% of patients treated with checkpoint inhibitors, but the underlying mechanisms for ircAEs are poorly understood. EXPERIMENTAL DESIGN: Phenotyping/biomarker analyses were conducted in 200 patients on checkpoint inhibitors [139 with ircAEs and 61 without (control group)] to characterize their clinical presentation and immunologic endotypes. Cytokines were evaluated in skin biopsies, skin tape strip extracts, and plasma using real-time PCR and Meso Scale Discovery multiplex cytokine assays. RESULTS: Eight ircAE phenotypes were identified: pruritus (26%), maculopapular rash (MPR; 21%), eczema (19%), lichenoid (11%), urticaria (8%), psoriasiform (6%), vitiligo (5%), and bullous dermatitis (4%). All phenotypes showed skin lymphocyte and eosinophil infiltrates. Skin biopsy PCR revealed the highest increase in IFNγ mRNA in patients with lichenoid (P < 0.0001) and psoriasiform dermatitis (P < 0.01) as compared with patients without ircAEs, whereas the highest IL13 mRNA levels were detected in patients with eczema (P < 0.0001, compared with control). IL17A mRNA was selectively increased in psoriasiform (P < 0.001), lichenoid (P < 0.0001), bullous dermatitis (P < 0.05), and MPR (P < 0.001) compared with control. Distinct cytokine profiles were confirmed in skin tape strip and plasma. Analysis determined increased skin/plasma IL4 cytokine in pruritus, skin IL13 in eczema, plasma IL5 and IL31 in eczema and urticaria, and mixed-cytokine pathways in MPR. Broad inhibition via corticosteroids or type 2 cytokine-targeted inhibition resulted in clinical benefit in these ircAEs. In contrast, significant skin upregulation of type 1/type 17 pathways was found in psoriasiform, lichenoid, bullous dermatitis, and type 1 activation in vitiligo. CONCLUSIONS: Distinct immunologic ircAE endotypes suggest actionable targets for precision medicine-based interventions.

Longitudinal quality of life after sublobar resection and stereotactic body radiation therapy for early-stage non-small cell lung cancer.

BACKGROUND: Many patients with early-stage lung cancer are not candidates for lobectomy because of various factors, with treatment options including sublobar resection or stereotactic body radiation therapy (SBRT). Limited information exists regarding patient-centered outcomes after these treatments. METHODS: Subjects with stage I-IIA non-small cell lung cancer (NSCLC) at high risk for lobectomy who underwent treatment with sublobar resection or SBRT were recruited from five medical centers. Quality of life (QOL) was compared with the Short Form 8 (SF-8) for physical and mental health and Functional Assessment of Cancer Therapy-Lung (FACT-L) surveys at baseline (pretreatment) and 7 days, 30 days, 6 months, and 12 months after treatment. Propensity score methods were used to control for confounders. RESULTS: Of 337 subjects enrolled before treatment, 63% received SBRT. Among patients undergoing resection, 89% underwent minimally invasive video-assisted thoracic surgery or robot-assisted resection. Adjusted analyses showed that SBRT-treated patients had both higher physical health SF-8 scores (difference in differences [DID], 6.42; p = .0008) and FACT-L scores (DID, 2.47; p = .004) at 7 days posttreatment. Mental health SF-8 scores were not different at 7 days (p = .06). There were no significant differences in QOL at other time points, and all QOL scores returned to baseline by 12 months for both groups. CONCLUSIONS: SBRT is associated with better QOL immediately posttreatment compared with sublobar resection. However, both treatment groups reported similar QOL at later time points, with a return to baseline QOL. These findings suggest that sublobar resection and SBRT have a similar impact on the QOL of patients with early-stage lung cancer deemed ineligible for lobectomy.

Discovery of MK-8189, a Highly Potent and Selective PDE10A Inhibitor for the Treatment of Schizophrenia.

PDE10A is an important regulator of striatal signaling that, when inhibited, can normalize dysfunctional activity. Given the involvement of dysfunctional striatal activity with schizophrenia, PDE10A inhibition represents a potentially novel means for its treatment. With the goal of developing PDE10A inhibitors, early optimization of a fragment hit through rational design led to a series of potent pyrimidine PDE10A inhibitors that required further improvements in physicochemical properties, off-target activities, and pharmacokinetics. Herein we describe the discovery of an isomeric pyrimidine series that addresses the liabilities seen with earlier compounds and resulted in the invention of compound 18 (MK-8189), which is currently in Phase 2b clinical development for the treatment of schizophrenia.

Adverse Events Following Limited Resection versus Stereotactic Body Radiation Therapy for Early Stage Lung Cancer.

Rationale: Approximately a quarter of patients with early stage lung cancer are not medically fit for lobectomy. Limited resection and stereotactic body radiation therapy (SBRT) have emerged as alternatives for these patients. Given the equipoise on the effectiveness of the two treatments, treatment-related adverse events (AEs) could have a significant impact on patients' decision-making and treatment outcomes. Objectives: To compare the AE profile between SBRT versus limited resection. Methods: Data were derived from a prospective cohort of patients with stage I-IIA non-small cell lung cancer who were deemed as high-risk for lobectomy recruited from five centers across the United States. Propensity scores and inverse probability weighting were used to compare the rates of 30- and 90-day AEs among patients treated with limited resection versus SBRT. Results: Overall, 65% of 252 patients underwent SBRT. After adjusting for propensity scores, there was no significant difference in developing at least one AE comparing SBRT to limited resection (odds ratio [OR]: 1.00; 95% confidence interval [CI]: 0.65-1.55 and OR: 1.27; 95% CI: 0.84-1.91 at 30 and 90 days, respectively). SBRT was associated with lower risk of infectious AEs than limited resection at 30 days (OR: 0.05; 95% CI: 0.01-0.39) and 90 days posttreatment (OR: 0.41; 95% CI: 0.17-0.98). Additionally, SBRT was associated with persistently elevated risk of fatigue (OR: 2.47; 95% CI: 1.34-4.54 at 30 days and OR: 2.69; 95% CI: 1.52-4.77 at 90 days, respectively), but significantly lower risks of respiratory AEs (OR: 0.36; 95% CI: 0.20-0.65 and OR: 0.51; 95% CI: 0.31-0.86 at 30 and 90 days, respectively). Conclusions: Though equivalent in developing at least one AE, we found that SBRT is associated with less toxicity than limited resection in terms of infectious and respiratory AEs but higher rates of fatigue that persisted up to 3 months posttreatment. This information, combined with data about oncologic effectiveness, can help patients' decision-making regarding these alternative therapies.

Beyond Steroids: Immunosuppressants in Steroid-Refractory or Resistant Immune-Related Adverse Events.

INTRODUCTION: The optimal management for immune-related adverse events (irAEs) in patients who do not respond or become intolerant to steroids is unclear. Guidelines suggest additional immunosuppressants on the basis of case reports and expert opinion. METHODS: We evaluated patients with lung cancers at Memorial Sloan Kettering Cancer Center treated with immune checkpoint blockade from 2011 to 2020. Pharmacy records were queried to identify patients who received systemic steroids and an additional immunosuppressant (e.g., tumor necrosis factor-α inhibitor, mycophenolate mofetil). Patient records were manually reviewed to evaluate baseline characteristics, management, and outcomes. RESULTS: Among 2750 patients with lung cancers treated with immune checkpoint blockade, 51 (2%) received both steroids and an additional immunosuppressant for a severe irAE (tumor necrosis factor-α inhibitor (73%), mycophenolate mofetil (20%)). The most common events were colitis (53%), pneumonitis (20%), hepatitis (12%), and neuromuscular (10%). At 90 days after the start of an additional immunosuppressant, 57% were improved from their irAE, 18% were unchanged, and 25% were deceased. Improvement was more common in hepatitis (five of six) and colitis (18 of 27) but less common in neuromuscular (one of five) and pneumonitis (3 of 10). Of the patients who died, 8 of 13 were attributable directly to the irAE and 4 of 13 were related to toxicity from immunosuppression (three infection-related deaths, one drug-induced liver injury leading to acute liver failure). CONCLUSIONS: Steroid-refractory or resistant irAEs events are rare. Although existing treatments help patients with hepatitis and colitis, many patients with other irAEs remain refractory or experience toxicities from immunosuppression. A more precise understanding of the pathophysiology of specific irAEs is needed to guide biologically-informed treatments for severe irAEs.

Our current understanding of checkpoint inhibitor therapy in cancer immunotherapy.

OBJECTIVE: Treatments with Food and Drug Administration-approved blocking antibodies targeting inhibitory cytotoxic T lymphocyte antigen 4 (CTLA4), programmed cell death protein 1 (PD-1) receptor, or programmed cell death ligand 1 (PD-L1), collectively named checkpoint inhibitors (CPIs), have been successful in producing long-lasting remissions, even in patients with advanced-stage cancers. However, these treatments are often accompanied by undesirable autoimmune and inflammatory side effects, sometimes bringing severe consequences for the patient. Rapid expansion of clinical applications necessitates a more nuanced understanding of CPI function in health and disease to develop new strategies for minimizing the negative side effects, while preserving the immunotherapeutic benefit. DATA SOURCES: This review summarizes a new paradigm-shifting approach to cancer immunotherapy with the focus on the mechanism of action of immune checkpoints (CTLA4, PD-1, and its ligands). STUDY SELECTIONS: We performed a literature search and identified relevant recent clinical reports, experimental research, and review articles. RESULTS: This review highlights our understanding of the CPI mechanism of action on cellular and molecular levels. The authors also discuss how reactivation of T cell responses through the inhibition of CTLA4, PD-1, and PD-L1 is used for tumor inhibition in cancer immunotherapy. CONCLUSION: Mechanisms of PD-1 and CTLA4 blockade and normal biological functions of these molecules are highly complex and require additional studies that will be critical for developing new approaches to dissociate the benefits of checkpoint blockade from off-target effects of the immune reactivation that leads to immune-related adverse events.

Immune-related cutaneous adverse events due to checkpoint inhibitors.

OBJECTIVE: To familiarize the reader with the most common cutaneous adverse events with immune checkpoint inhibitors (CPIs) and their grading and treatment. DATA SOURCES: Recent research articles, relevant review articles, and case series/reports in English from the PubMed database mostly, from 2010 onward. STUDY SELECTIONS: Most data are from retrospective studies and case series. Older studies regarding the mechanism were included if they were of particular importance. RESULTS: An understanding of this review should enable the reader to identify specific skin disorders in patients receiving immune CPIs, grade the adverse event, and be able to treat or refer the patient as needed. CONCLUSION: Allergists/immunologists need to be familiar with these immune-related cutaneous adverse events because their incidence will increase with the ever-expanding use of CPIs and, in particular, because patients will certainly continue to be referred suspecting drug allergies.

Structures of active-state orexin receptor 2 rationalize peptide and small-molecule agonist recognition and receptor activation.

Narcolepsy type 1 (NT1) is a chronic neurological disorder that impairs the brain's ability to control sleep-wake cycles. Current therapies are limited to the management of symptoms with modest effectiveness and substantial adverse effects. Agonists of the orexin receptor 2 (OX2R) have shown promise as novel therapeutics that directly target the pathophysiology of the disease. However, identification of drug-like OX2R agonists has proven difficult. Here we report cryo-electron microscopy structures of active-state OX2R bound to an endogenous peptide agonist and a small-molecule agonist. The extended carboxy-terminal segment of the peptide reaches into the core of OX2R to stabilize an active conformation, while the small-molecule agonist binds deep inside the orthosteric pocket, making similar key interactions. Comparison with antagonist-bound OX2R suggests a molecular mechanism that rationalizes both receptor activation and inhibition. Our results enable structure-based discovery of therapeutic orexin agonists for the treatment of NT1 and other hypersomnia disorders.

Epipericardial Fat Pad Necrosis-A Rare Cause of Chest Pain in an Adolescent.

ABSTRACT: Epipericardial fat necrosis is a rare cause of acute pleuritic chest pain reported in approximately 40 cases. This diagnosis mimics a myocardial infarction, pulmonary embolism, or pericarditis; however, the cardiac enzymes and electrocardiogram are usually normal. We present the first reported case of epipericardial fat necrosis in an adolescent.

Role of mTOR As an Essential Kinase in SCLC.

OBJECTIVES: SCLC represents 15% of all lung cancer diagnoses in the United States and has a particularly poor prognosis. We hypothesized that kinases regulating SCLC survival pathways represent therapeutically targetable vulnerabilities whose inhibition may improve SCLC outcome. METHODS: A short-hairpin RNA (shRNA) library targeting all human kinases was introduced in seven chemonaive patient-derived xenografts (PDX) and the cells were cultured in vitro and in vivo. On harvest, lost or depleted shRNAs were considered as regulating-cell survival pathways and deemed essential kinases. RESULTS: Unsupervised hierarchical cluster analysis of recovered shRNAs separated the PDXs into two clusters, suggesting kinase-based heterogeneity among the SCLC PDXs. A total of 23 kinases were identified as essential in two or more PDXs, with mechanistic Target of Rapamycin (mTOR) a candidate essential kinase in four. mTOR phosphorylation status correlated with PDX sensitivity to mTOR kinase inhibition, and mTOR inhibition sensitized the PDX to cisplatin and etoposide. In the PDX in which mTOR was defined as essential, mTOR inhibition caused a 43% decrease in tumor volume at 21 days (p < 0.01). Combining mTOR inhibition with cisplatin and etoposide decreased PDX tumor volume 96% compared with cisplatin and etoposide alone at 70 days (p < 0.002). Chemoresistance did not develop with the combination of mTOR inhibition and cisplatin and etoposide in mTOR-essential PDX over 105 days. The prevalence of phospho-mTOR-Ser-2448 in a tissue microarray of chemonaive SCLC was 27%, thus, identifying an important SCLC subtype that might benefit from the addition of mTOR inhibition to standard chemotherapy. CONCLUSIONS: These studies reveal that kinases can define SCLC subgroups, can identify therapeutic vulnerabilities, and can potentially be used to optimize therapeutic approaches. Significance We used functional genomics to identify kinases regulating SCLC survival. mTOR was identified as essential in a subset of PDXs. mTOR inhibition decreased PDX growth, sensitized PDX to cisplatin and etoposide, and prevented chemoresistance.

Immune checkpoint inhibitor-related dermatologic adverse events.

Immune checkpoint inhibitors have emerged as a pillar in the management of advanced malignancies. However, nonspecific immune activation may lead to immune-related adverse events, wherein the skin and its appendages are the most frequent targets. Cutaneous immune-related adverse events include a diverse group of inflammatory reactions, with maculopapular rash, pruritus, psoriasiform and lichenoid eruptions being the most prevalent subtypes. Cutaneous immune-related adverse events occur early, with maculopapular rash presenting within the first 6 weeks after the initial immune checkpoint inhibitor dose. Management involves the use of topical corticosteroids for mild to moderate (grades 1-2) rash, addition of systemic corticosteroids for severe (grade 3) rash, and discontinuation of immunotherapy with grade 4 rash. Bullous pemphigoid eruptions, vitiligo-like skin hypopigmentation/depigmentation, and psoriasiform rash are more often attributed to programmed cell death-1/programmed cell death ligand-1 inhibitors. The treatment of bullous pemphigoid eruptions is similar to the treatment of maculopapular rash and lichenoid eruptions, with the addition of rituximab in grade 3-4 rash. Skin hypopigmentation/depigmentation does not require specific dermatologic treatment aside from photoprotective measures. In addition to topical corticosteroids, psoriasiform rash may be managed with vitamin D3 analogues, narrowband ultraviolet B light phototherapy, retinoids, or immunomodulatory biologic agents. Stevens-Johnson syndrome and other severe cutaneous immune-related adverse events, although rare, have also been associated with checkpoint blockade and require inpatient care as well as urgent dermatology consultation.

Interleukin-6 is required for Neuregulin-1 induced HER2 signaling in lung epithelium.

A clear understanding of the mechanisms that regulate the alveolar epithelium's barrier is critical to develop new therapeutic strategies to mitigate lung injury. The HER2/HER3 receptor tyrosine kinase complex plays a central role in maintaining the alveolar-capillary barrier. This receptor complex is activated by its ligand, neuregulin-1 (NRG-1). Interleukin-6 (IL-6) is also known to induce HER2 signaling through HER2 transphosphorylation by the IL-6 receptor (IL-6R) complex (1). Due to this interaction, we hypothesized that NRG-1 and IL-6 cooperatively interacted to activate the HER2/HER3 complex. Studies were performed in cultured pulmonary epithelial cells measuring the HER2/IL-6/IL-6R/GP130 interaction and receptor activation by western blotting and confocal microscopy, IL-6 production by ELISA, and IL-6 inhibition using specific antibodies, small molecule inhibitors and shRNA. We found that IL-6 was required for NRG-1 induced activation of HER2 in pulmonary epithelial cells. IL-6 inhibition led to a decrease in NRG-1 induced HER2 activation. The IL-6R and GP130, a subunit of the IL-6R complex, were physically associated with HER2 and were required for NRG-1 induced HER2 activation. Inhibition of GP130, the ß-subunit of the IL-6 receptor decreased NRG-1 induced HER2 activation lower than control by 38% Finally, HER2 activation increased IL-6 secretion more than two-fold over resting cells (526 ± 131 vs 231 ± 39.7 pg/ml), and inhibition of HER2 gene expression decreased basal IL-6 secretion over 80% (89 + 4.6 vs 1.3 + 0.8 pg/ml). These findings identify a requirement for IL-6 and the IL-6R complex to allow NRG-1 mediated HER2 activation, and a HER2 driven IL-6 production feedback loop.

The Kinome of Human Alveolar Type II and Basal Cells, and Its Reprogramming in Lung Cancer.

The discovery of mutant tyrosine kinases as oncogenic drivers of lung adenocarcinomas has changed the basic understanding of lung cancer development and therapy. Yet, expressed kinases (kinome) in lung cancer progenitor cells, as well as whether kinase expression and the overall kinome changes or is reprogrammed upon transformation, is incompletely understood. We hypothesized that the kinome differs between lung cancer progenitor cells, alveolar type II cells (ATII), and basal cells (BC) and that their respective kinomes undergo distinct lineage-specific reprogramming to adenocarcinomas and squamous cell carcinomas upon transformation. We performed RNA sequencing on freshly isolated human ATII, BC, and lung cancer cell lines to define the kinome in nontransformed cells and transformed cells. Our studies identified a unique kinome for ATII and BC and changes in their kinome upon transformation to their respective carcinomas.

Development of Anti-CD74 Antibody-Drug Conjugates to Target Glucocorticoids to Immune Cells.

Glucocorticoids (GCs) are excellent anti-inflammatory drugs but are dose-limited by on-target toxicity. We sought to solve this problem by delivering GCs to immune cells with antibody-drug conjugates (ADCs) using antibodies containing site-specific incorporation of a non-natural amino acid, novel linker chemistry for in vitro and in vivo stability, and existing and novel glucocorticoid receptor (GR) agonists as payloads. We directed fluticasone propionate to human antigen-presenting immune cells to afford GR activation that was dependent on the targeted antigen. However, mechanism of action studies pointed to accumulation of free payload in the tissue culture supernatant as the dominant driver of activity and indeed administration of the ADC to human CD74 transgenic mice failed to activate GR target genes in splenic B cells. Suspecting dissipation of released payload, we designed an ADC bearing a novel GR agonist payload with reduced permeability which afforded cell-intrinsic activity in human B cells. Our work shows that antibody-targeting offers significant potential for rescuing existing and new dose-limited drugs outside the field of oncology.

Association Between Baseline Blood Pressures, Heart Rates, and Vasovagal Syncope in Children and Adolescents.

BACKGROUND: Vasovagal syncope is the most common cause of syncope in children and adults, accounting for 50-66% of unexplained syncope. There are no studies establishing the relationship between syncope, baseline heart rate, and blood pressure. OBJECTIVE: To identify a possible association between baseline blood pressure and heart rate with syncope. DESIGN/METHODS: We conducted a questionnaire-based chart review study. A questionnaire was distributed to the guardian of children between eight and 18 years of age who attended the Pediatric Ambulatory Care Clinic at Flushing Hospital Medical Center. Based on the responses in the questionnaire, subjects were classified either as cases (positive for syncope) or controls (negative for syncope). Children and adolescents with neurological, cardiac, or any medical condition that can cause syncopal episodes were excluded from the study. Data collected from the questionnaire included age, gender, ethnicity, medical history, family history of syncope, and the amount of salt used in food. Anthropometric and vital signs for the current visit (height, weight, BMI, blood pressure, and heart rate) and vital signs from two previous visits were collected from electronic medical records. The data was analyzed using t-test and chi-square test with Microsoft Excel software (Microsoft Office Standard, v. 14, Microsoft; 2010); p<0.05 was considered significant. RESULTS: A total of 197 subjects were included in this study. There were 18 cases and 179 controls. Of the cases, (4/18) 22.2% were more likely to have a systolic blood pressure lower than the 10th percentile for their gender, age, and height as compared with controls (7/179) 3.9%, p = 0.003. The subjects with a history of syncope were more likely to add salt to their food (p = 0.004). There were no significant differences between cases and controls for age, gender, ethnicity between cases and controls for systolic blood pressure. No significant difference was observed between the heart rates of cases and controls. CONCLUSIONS: Children and adolescents with syncope were more likely to have a systolic blood pressure lower than the 10th percentile, and there was no difference in the baseline heart rate. In addition, children with syncope were more likely to add salt to their food.

Antigen-Presenting Intratumoral B Cells Affect CD4+ TIL Phenotypes in Non-Small Cell Lung Cancer Patients.

Effective immunotherapy options for patients with non-small cell lung cancer (NSCLC) are becoming increasingly available. The immunotherapy focus has been on tumor-infiltrating T cells (TILs); however, tumor-infiltrating B cells (TIL-Bs) have also been reported to correlate with NSCLC patient survival. The function of TIL-Bs in human cancer has been understudied, with little focus on their role as antigen-presenting cells and their influence on CD4+ TILs. Compared with other immune subsets detected in freshly isolated primary tumors from NSCLC patients, we observed increased numbers of intratumoral B cells relative to B cells from tumor-adjacent tissues. Furthermore, we demonstrated that TIL-Bs can efficiently present antigen to CD4+ TILs and alter the CD4+ TIL phenotype using an in vitro antigen-presentation assay. Specifically, we identified three CD4+ TIL responses to TIL-Bs, which we categorized as activated, antigen-associated, and nonresponsive. Within the activated and antigen-associated CD4+ TIL population, activated TIL-Bs (CD19+CD20+CD69+CD27+CD21+) were associated with an effector T-cell response (IFNγ+ CD4+ TILs). Alternatively, exhausted TIL-Bs (CD19+CD20+CD69+CD27-CD21-) were associated with a regulatory T-cell phenotype (FoxP3+ CD4+ TILs). Our results demonstrate a new role for TIL-Bs in NSCLC tumors in their interplay with CD4+ TILs in the tumor microenvironment, establishing them as a potential therapeutic target in NSCLC immunotherapy. Cancer Immunol Res; 5(10); 898-907. ©2017 AACR.

Diffuse Idiopathic Pulmonary Neuroendocrine Cell Hyperplasia and Neuroendocrine Hyperplasia of Infancy.

Although incidental reactive pulmonary neuroendocrine cell hyperplasia (PNECH) is seen on biopsy specimens in adults with chronic lung disease, disorders characterized by marked PNECH are rare. Primary hyperplasia of neuroendocrine cells in the lung and obstructive lung disease related to remodeling or physiologic constriction of small airways define diffuse idiopathic neuroendocrine cell hyperplasia (DIPNECH) in the adult and neuroendocrine cell hyperplasia of infancy (NEHI) in children. DIPENCH and NEHI share a similar physiology, typical imaging appearance, and increased neuroendocrine cells on biopsy. However, there are important differences related to the underlying disease mechanisms leading to disparate outcomes.

Novel Phosphate Modified Cathepsin B Linkers: Improving Aqueous Solubility and Enhancing Payload Scope of ADCs.

In an effort to examine the utility of antibody-drug conjugates (ADCs) beyond oncology indications, a novel phosphate bridged Cathepsin B sensitive linker was developed to enable the targeted delivery of glucocorticoids. Phosphate bridging of the Cathepsin B sensitive linkers allows for payload attachment at an aliphatic alcohol. As small molecule drug-linkers, these aqueous soluble phosphate containing drug-linkers were found to have robust plasma stability coupled with rapid release of payload in a lysosomal environment. Site-specific ADCs were successfully made between these drug-linkers and an antibody against human CD70, a receptor specifically expressed in immune cells but also found aberrantly expressed in multiple human carcinomas. These ADCs demonstrated in vitro targeted delivery of glucocorticoids to a representative cell line as measured by changes in glucocorticoid receptor (GR) mediated gene mRNA levels. This novel linker expands the scope of potential ADC payloads by allowing an aliphatic alcohol to be a stable, yet cleavable attachment site. This phosphate linker may have broad utility for internalizing ADCs as well as other targeted delivery platforms.

Discovery of Pyrophosphate Diesters as Tunable, Soluble, and Bioorthogonal Linkers for Site-Specific Antibody-Drug Conjugates.

As part of an effort to examine the utility of antibody-drug conjugates (ADCs) beyond oncology indications, a novel pyrophosphate ester linker was discovered to enable the targeted delivery of glucocorticoids. As small molecules, these highly soluble phosphate ester drug linkers were found to have ideal orthogonal properties: robust plasma stability coupled with rapid release of payload in a lysosomal environment. Building upon these findings, site-specific ADCs were made between this drug linker combination and an antibody against human CD70, a receptor specifically expressed in immune cells but also found aberrantly expressed in multiple human carcinomas. Full characterization of these ADCs enabled procession to in vitro proof of concept, wherein ADCs 1-22 and 1-37 were demonstrated to afford potent, targeted delivery of glucocorticoids to a representative cell line, as measured by changes in glucocorticoid receptor-mediated gene mRNA levels. These activities were found to be antibody-, linker-, and payload-dependent. Preliminary mechanistic studies support the notion that lysosomal trafficking and enzymatic linker cleavage are required for activity and that the utility for the pyrophosphate linker may be general for internalizing ADCs as well as other targeted delivery platforms.