Self-Immolative Carbamate Linkers for CD19-Budesonide Antibody-Drug Conjugates.

Antibody-drug conjugates consist of potent small-molecule payloads linked to a targeting antibody. Payloads must possess a viable functional group by which a linker for conjugation can be attached. Linker-attachment options remain limited for the connection to payloads via hydroxyl groups. A releasing group based on 2-aminopyridine was developed to enable stable attachment of para-aminobenzyl carbamate (PABC) linkers to the C21-hydroxyl group of budesonide, a glucocorticoid receptor agonist. Payload release involves a cascade of two self-immolative events that are initiated by the protease-mediated cleavage of the dipeptide-PABC bond. Budesonide release rates were determined for a series of payload-linker intermediates in buffered solution at pH 7.4 and 5.4, leading to the identification of 2-aminopyridine as the preferred releasing group. Addition of a poly(ethylene glycol) group improved linker hydrophilicity, thereby providing CD19-budesonide ADCs with suitable properties. ADC23 demonstrated targeted delivery of budesonide to CD19-expressing cells and inhibited B-cell activation in mice.

Targeting the Tyrosine Kinase 2 (TYK2) Pseudokinase Domain: Discovery of the Selective TYK2 Inhibitor ABBV-712.

Tyrosine kinase 2 (TYK2) is a nonreceptor tyrosine kinase that belongs to the JAK family also comprising JAK1, JAK2, and JAK3. TYK2 is an attractive target for various autoimmune diseases as it regulates signal transduction downstream of IL-23 and IL-12 receptors. Selective TYK2 inhibition offers a differentiated clinical profile compared to currently approved JAK inhibitors. However, selectivity for TYK2 versus other JAK family members has been difficult to achieve with small molecules that inhibit the catalytically active kinase domain. Successful targeting of the TYK2 pseudokinase domain as a strategy to achieve isoform selectivity was recently exemplified with deucravacitinib. Described herein is the optimization of selective TYK2 inhibitors targeting the pseudokinase domain, resulting in the discovery of the clinical candidate ABBV-712 (21).

Quenching mechanism of Zn(salicylaldimine) by nitroaromatics.

Nitroaromatics and nitroalkanes quench the fluorescence of Zn(Salophen) (H2Salophen = N,N'-phenylene-bis-(3,5-di- tert-butylsalicylideneimine); ZnL(R)) complexes. A structurally related family of ZnL(R) complexes (R = OMe, di-tBu, tBu, Cl, NO2) were prepared, and the mechanisms of fluorescence quenching by nitroaromatics were studied by a combined kinetics and spectroscopic approach. The fluorescent quantum yields for ZnL(R) were generally high (Phi approximately 0.3) with sub-nanosecond fluorescence lifetimes. The fluorescence of ZnL(R) was quenched by nitroaromatic compounds by a mixture of static and dynamic pathways, reflecting the ZnL(R) ligand bulk and reduction potential. Steady-state Stern-Volmer plots were curved for ZnL(R) with less-bulky substituents (R = OMe, NO2), suggesting that both static and dynamic pathways were important for quenching. Transient Stern-Volmer data indicated that the dynamic pathway dominated quenching for ZnL(R) with bulky substituents (R = tBu, DtBu). The quenching rate constants with varied nitroaromatics (ArNO2) followed the driving force dependence predicted for bimolecular electron transfer: ZnL* + ArNO2 --> ZnL(+) + ArNO2(-). A treatment of the diffusion-corrected quenching rates with Marcus theory yielded a modest reorganization energy (lambda = 25 kcal/mol), and a small self-exchange reorganization energy for ZnL*/ZnL(+) (ca. 20 kcal/mol) was estimated from the Marcus cross-relation, suggesting that metal phenoxyls may be robust biological redox cofactors. Electronic structure calculations indicated very small changes in bond distances for the ZnL --> ZnL(+) oxidation, suggesting that solvation was the dominant contributor to the observed reorganization energy. These mechanistic insights provide information that will be helpful to further develop ZnL(R) as sensors, as well as for potential photoinduced charge transfer chemistry.

Fluorescent detection of nitroaromatics and 2,3-dimethyl 2,3-dinitrobutane (DMNB) by a zinc complex: (salophen)Zn.

Fluorescent sensors for the detection of chemical explosives are in great demand. It is shown herein that the fluorescence of ZnL* (H2L=N,N'-phenylene-bis-(3,5-di-tert-butylsalicylideneimine)) is quenched in solution by nitroaromatics and 2,3-dimethyl-2,3-dinitrobutane (DMNB), chemical signatures of explosives. The relationship between the structure and fluorescence of ZnL is explored, and crystal structures of three forms of ZnL(base), (base=ethanol, tetrahydrofuran, pyridine) are reported, with the base=ethanol structure exhibiting a four-centered hydrogen bonding array. Solution structures are monitored by 1H NMR and molecular weight determination, revealing a dimeric structure in poor donor solvents which converts to a monomeric structure in the presence of good donor solvents or added Lewis bases to form five-coordinate ZnL(base). Fluorescence wavelengths and quantum yields in solution are nearly insensitive to monomer-dimer interconversion, as well as to the identity of the Lewis base; in contrast, the emission wavelength in the solid state varies for different ZnL(base) due to pi-stacking. Nitroaromatics and DMNB are moderately efficient quenchers of ZnL*, with Stern-Volmer constants KSV=2-49 M-1 in acetonitrile solution.

Is cardiac catheterization a prerequisite in all patients undergoing bidirectional cavopulmonary anastomosis?

Traditionally, all patients undergo cardiac catheterization before bidirectional cavopulmonary anastomosis (BCPA). The purpose of this study was to determine if preoperative catheterization is necessary when echocardiographic parameters appear favorable. A retrospective review was performed of all patients who underwent BCPA (n = 142) between February 1996 and May 2001. Echocardiographic criteria defining a favorable BCPA candidate included good ventricular function, moderate or less atrioventricular and semilunar valve regurgitation, absence of ventricular outflow tract obstruction, normal proximal branch pulmonary artery (PA) size, and low PA pressures estimated by PA band gradient or systemic PA shunt velocity. The median age at operation was 7 months (range: 2-11) and weight was 6.2 kg (range: 2.7-7.1). There were 73 unfavorable candidates. Patients with hypoplastic left heart syndrome (n = 23) and pulmonary atresia with intact septum (n = 15) predominated among the unfavorable group. All patients were catheterized. This provided additional information on PA pressures in 3 patients in the favorable group but did not defer operation or influence outcome (no mortality, prolonged pleural drainage, or longer intensive care department stay). All 3 patients are alive at a mean follow-up of 51 months. The 30-day mortality was 2% (4 of 151 patients), all in the unfavorable group. Overall, 20 patients (13%) required arterioplasty of PAs at the time of BCPA. BCPA can be performed with a low risk of morbidity and mortality in a wide range of patients. By using commonly acquired echocardiographic parameters, a low-risk subgroup of patients can be identified who can safely avoid preoperative cardiac catheterization.

Cardiac catheterisation in infants weighing less than 2500 grams.

OBJECTIVES: To investigate the indications for, and outcome of, cardiac catheterisation in infants weighing less than 2500 g at a single institution over an 8-year period. PATIENTS AND METHODS: We assessed all infants who were less than 2500 g at the time of cardiac catheterisation at Texas Children's Hospital from January 1993 to January 2001. Comparisons of morbidity and mortality were drawn with an equivalent number of infants of similar age weighing greater than 2500 g seen over the same period of time. RESULTS: We performed interventional procedures in 22, and diagnostic catheterisations in 12 infants weighing less than 2500 g. Interventions included pulmonary valvoplasty in six patients, balloon angioplasty of critical coarctation in one, aortic valvoplasty in two, septostomy in ten, and coil occlusion of an arteriovenous malformation, redirection of a subclavian venous line, and coil occlusion of a patent arterial duct in one patient each. The median age at catheterisation was 5 days for children less than 2500 g, and 10 days for those above 2500 g. The median weights were 2.3 kg and 3.3 kg, and the median gestational ages were 35 weeks and 38 weeks, for the two respective groups. Of those weighing less than 2500 g, two died (6%), with no deaths occurring in those weighing more than 2500 g. In 3 patients weighing less than 2500 g (9%), there was vascular compromise, one child with bilateral femoral venous obstruction requiring fasciotomy compared, to one in the group weighing greater than 2500 g (2%). CONCLUSION: There is a significantly increased risk of mortality and vascular compromise in infants weighing less than 2500 g. Interventional catheterisation in these infants may be lifesaving, but given the aforementioned risks, diagnostic catheterisation should be deferred if possible in favor of noninvasive modalities.

Echocardiographic presentations of endocarditis, and risk factors for rupture of a sinus of Valsalva in childhood.

BACKGROUND: In recent years, the diagnosis of infective endocarditis has been enhanced by the use of echocardiography. We sought, therefore, to review its effect on the management of endocarditis in children. METHODS: We reviewed all the patients presenting to our institution for evaluation for infective endocarditis from May 1994 to January 2002. The patients were stratified according to whether or not they had congenitally malformed hearts. RESULTS: Of the 90 referred patients identified, 46 (51%) had positive ultrasonic findings. Of these, we excluded 26 patients because of the presence of indwelling lines. The remaining 20 patients with features of endocarditis had a median age of 6.5 years, and a range from 0.14 to 8.5 years. There were 4 patients with normal hearts, and 16 with congenital cardiac malformations. We identified rupture of a sinus of Valsalva in four patients, with rupture into the left ventricle in two, and into the right ventricle and right atrium in one each. The mitral valve was involved in six patients, the aortic valve in another six, including all four with rupture of the sinus of Valsalva, both mitral and aortic valves in three, the pulmonary trunk in three patients, and the tricuspid valve and a Blalock-Taussig shunt in one patient each. Organisms isolated included Streptococcus mitis in 4 patients, Streptococcus pneumoniae in 2 patients, Streptococcus sanguis in 1, Staphylococcus aureus in 3, Staphylococcus epidermidis in 1, and Enteroccocus in 2. Cultures proved negative in 7 patients. Surgical intervention was needed in 12 patients, and one died (5%). Only the left-sided chambers were involved in those with normal hearts. Both patients infected with Streptococcus pneumoniae had rupture of a sinus of Valsalva. CONCLUSION: Involvement of the left-sided chambers is more likely in structurally normal hearts, and in cases with rupture of a sinus of Valsalva, in which case infection with Streptococcus pneumonia should be suspected.

Pericardial effusion and tamponade in infants with central catheters.

OBJECTIVE: To describe the clinical presentation, cause, and outcome of central venous catheter (CVC)-related pericardial effusions (PCE) in infants. METHODS: A retrospective case review was conducted of CVC-related PCE at university and private neonatal intensive care units. Data from our cases were combined with published case reports and included clinical presentation and outcome; biochemical evaluation of pericardial fluid; days until diagnosis; cardiothoracic ratios; and CVC characteristics, insertion site, and tip placement site. RESULTS: In our cases, 6 different neonatology groups cared for 14 patients at 6 different hospitals in 2 cities. These data were combined with 47 cases reviewed from the literature. Pericardial fluid was obtained in 54 cases from the combined group and was described qualitatively as consistent with the infusate in 53 of 54 cases (98%). Biochemical analysis was performed in 37 cases, and in 36 of 37 cases (97%), the pericardial fluid was consistent with the infusate. The median gestational age at birth was 30.0 weeks (range: 23.5-42). The median time from CVC insertion to diagnosis was 3.0 days (range: 0.2-37; n = 59). Sudden cardiac collapse was reported in 37 cases (61%), and unexplained cardiorespiratory instability was reported in 22 cases (36%). The CVC tip was last reported within the pericardial reflections on chest radiograph in 56 cases (92%) at the time of PCE diagnosis. The mean cardiothoracic ratio increased 17% (n = 14). No patients died among our cases. Among the reviewed cases, 45% mortality was reported. For the combined group, mortality was 34%. For the combined group, mortality was 8% (3 of 37) in the patients who underwent pericardiocentesis versus 75% (18 of 24) for the patients who did not. In 21 patients, the catheter was withdrawn and remained in use. Survivors and nonsurvivors had comparable gestational age at birth, birth weight, days to PCE diagnosis, and day of life of PCE symptoms/diagnosis. Access site, catheter type, and catheter size were not associated with mortality. An association between larger catheters and shorter time to PCE may be present. Access site and catheter type were not associated with time to PCE. Autopsy specimens reported 6 cases of myocardial necrosis/thrombus formation, 9 cases of perforation without myocardial necrosis/thrombus formation, and 2 cases in which both were reported. CONCLUSIONS: The pericardial fluid found in CVC-associated PCE is consistent with the infusate. We speculate that there are several mechanisms, ranging from frank perforation that seals spontaneously to CVC tip adhesion to the myocardium with diffusion into the pericardial space. Routine radiography should be performed, and the CVC tip should be readily identifiable. The CVC tip should remain outside the cardiac silhouette but still within the vena cavae (approximately 1 cm outside the cardiac silhouette in premature infants and 2 cm in term infants). A change in cardiothoracic ratio may be diagnostic of a PCE, and pericardiocentesis is associated with significantly reduced mortality. Increased awareness of this complication may decrease the mortality associated with CVC-related PCE.

SUCCESSFUL SURGICAL MANAGEMENT OF CONGENITAL ARTERIOVENOUS FISTULA OF THE SUBCLAVIAN ARTERY: CASE REPORT.

A 10-month-old infant was found to have an isolated congenital arteriovenous fistula between the right subclavian artery and vein. Ligation of the fistula resulted in complete anatomic correction and rapid resolution of cardiomegaly.