Epitope topography of agonist antibodies to the checkpoint inhibitory receptor BTLA

B and T lymphocyte attenuator (BTLA) is an attractive target for a new class of therapeutics that attempt to rebalance the immune system by agonizing checkpoint inhibitory receptors (CIRs). Herpesvirus entry mediator (HVEM) binds BTLA in both trans- and cis-orientations. We report here the development and structural characterization of three humanized BTLA agonist antibodies, 22B3, 25F7, and 23C8. We determined the crystal structures of the antibody-BTLA complexes, showing that these antibodies bind distinct and non-overlapping epitopes of BTLA. While all three antibodies activate BTLA, 22B3 mimics HVEM binding to BTLA and shows the strongest agonistic activity in functional cell assays and in an imiquimod-induced mouse model of psoriasis. 22B3 is also capable of modulating HVEM signaling through the BTLA-HVEM cis-interaction. The data obtained from crystal structures, biochemical assays, and functional studies provide a mechanistic model of HVEM and BTLA organization on the cell surface and informed the discovery of a highly active BTLA agonist.

Computational stabilization of T cell receptors allows pairing with antibodies to form bispecifics

Recombinant T cell receptors (TCRs) can be used to redirect naïve T cells to eliminate virally infected or cancerous cells; however, they are plagued by low stability and uneven expression. Here, we use molecular modeling to identify mutations in the TCR constant domains (Cα/Cβ) that increase the unfolding temperature of Cα/Cβ by 20 °C, improve the expression of four separate α/β TCRs by 3- to 10-fold, and improve the assembly and stability of TCRs with poor intrinsic stability. The stabilizing mutations rescue the expression of TCRs destabilized through variable domain mutation. The improved stability and folding of the TCRs reduces glycosylation, perhaps through conformational stabilization that restricts access to N-linked glycosylation enzymes. The Cα/Cβ mutations enables antibody-like expression and assembly of well-behaved bispecific molecules that combine an anti-CD3 antibody with the stabilized TCR. These TCR/CD3 bispecifics can redirect T cells to kill tumor cells with target HLA/peptide on their surfaces in vitro.

Aurora A Kinase Inhibition Is Synthetic Lethal with Loss of the RB1 Tumor Suppressor Gene

Loss-of-function mutations in the retinoblastoma gene RB1 are common in several treatment-refractory cancers such as small-cell lung cancer and triple-negative breast cancer. To identify drugs synthetic lethal with RB1 mutation (RB1 ^mut), we tested 36 cell-cycle inhibitors using a cancer cell panel profiling approach optimized to discern cytotoxic from cytostatic effects. Inhibitors of the Aurora kinases AURKA and AURKB showed the strongest RB1 association in this assay. LY3295668, an AURKA inhibitor with over 1,000-fold selectivity versus AURKB, is distinguished by minimal toxicity to bone marrow cells at concentrations active against RB1 ^mut cancer cells and leads to durable regression of RB1 ^mut tumor xenografts at exposures that are well tolerated in rodents. Genetic suppression screens identified enforcers of the spindle-assembly checkpoint (SAC) as essential for LY3295668 cytotoxicity in RB1-deficient cancers and suggest a model in which a primed SAC creates a unique dependency on AURKA for mitotic exit and survival. SIGNIFICANCE: The identification of a synthetic lethal interaction between RB1 and AURKA inhibition, and the discovery of a drug that can be dosed continuously to achieve uninterrupted inhibition of AURKA kinase activity without myelosuppression, suggest a new approach for the treatment of RB1-deficient malignancies, including patients progressing on CDK4/6 inhibitors.See related commentary by Dick and Li, p. 169.This article is highlighted in the In This Issue feature, p. 151.

Trisilane-1,3-diolato Complexes of Ti and Zr: Syntheses and X-ray Crystal Structures

The syntheses and structures of zirconium and titanium complexes containing the novel chelating trisilane-1,3-diolate ligand [Me2Si(R2SiO)2]2- (R = SiMe3) (5)-H2 are reported. The chloride complexes [Me2Si(R2SiO)2]TiCl2 (7a) and [Me2Si(R2SiO)2]ZrCl2 x 2 THF (7b) were prepared by the reaction of MCl4 (M = Ti, Zr) with [Me2Si(R2SiO)2]2Ti (6a) and [Me2Si(R2SiO)2]2Zr (6b), which are derived from the reaction of 5 with M(NEt2)4, respectively. In the presence of TiCl4, complexes 6a and 7a undergo a ring-opening reaction to produce the dinuclear complex [Me2Si(R2SiO)2][TiCl3]2 (9). [Me2Si(R2SiO)2]TiMe2 (10) and [Me2Si(R2SiO)2]TiBnz2 (11) were prepared in moderate yields from reactions of 7a with 2 equiv of MeMgBr and BnzMgCl, respectively. According to NMR spectroscopic investigations, the reaction of the dimethyltitanium complex 10 with B(C6F5)3 led to full exchange of both methyl groups by C6F5 groups under quantitative formation of [Me2Si(R2SiO)2]Ti(C6F5)2 (12) and a mixture of B(C6F5)(3-n)Me(n), where n = 1-3. The structure of 12 is further evidenced by the preparation of an identical sample from the reaction of 7a with 2 equiv of C6F5MgBr. Refluxing an ether solution of 12 surprisingly gave [Me2Si(R2SiO)2]2TiC6F5]2O (13) as a result of ether cleavage. The structures of the complexes 7a, 7b, 9, 10, and 13 were determined by X-ray crystallography, and structural discussion of the bond parameters will be given.

[Genital findings in sexually abused prepubertal girls]

Genital findings in sexually abused prepubertal girls. Childhood sexual abuse is defined as the involvement of dependent, developmentally immature children and adolescents in sexual activities that they do not fully comprehend, to which they are unable to give informed consent or that violate the social taboos of family roles. Essential to the diagnosis of sexual abuse is an awareness of the problem and acknowledgement of its manifestations. The evaluation of the sexually abused girl usually is performed in a pediatric and adolescent gynecology outpatient department. Thus, the gynecologist will be part of a multidisciplinary approach to the problem and will need to be competent in the basic skills of history taking, physical examination, selection of laboratory tests und differential diagnosis. Findings secondary to sexual abuse are often subtle. Acute tears or bruisings are rare, because force is seldom part of sexual acts committed against a child. A vaginal opening of greater than 5 mm is not common and may indicate vaginal penetration. An intact hymen not necessarily exclude vaginal intercourse. Lack of physical evidence never rules out abuse because sexual acts may leave no physical findings.

Identification of a sperm receptor-glycoprotein from the porcine zona pellucida

Porcine zona pellucida were solubilized by treatment with lithium 3,5-diiodosalicylate. Following further purification by phenol/water extraction, ethanol precipitation and high performance liquid chromatography a total of 11 fractions were obtained. Fractions in the molecular mass range, that were previously found to possess antigenic properties, were tested in a spermatozoa radio-receptor binding assay. One of the fractions with an N-terminal amino-acid residue of alanine was found to have spermatozoa receptor properties. This result might aid future studies on the spermatozoazona pellucida interactions at the molecular level.

[The EEG and its correlation with the intermittent vertebrobasilar syndrome]

A total of 325 patients with an intermittent vertebrobasilar insufficiency syndrome were subjected to electroencephalography. Certain characteristic features could be determined. Dominant among pathological findings were beta wave frequency bands in females. Normal electroencephalograms were obtained especially in males. There was frequently observed a low level of brain potentials, but this should not be regarded as an obligate criterion. Correlation of the electroencephalogram with the clinical syndrome was only possible by taking into account the patient's medical history and by taking additional diagnostic measures, more especially as other processes in the middle and posterior cranial fossae also tended to produce corresponding changes in electroencephalograms. Also dealth with by the author in his present paper are pathophysiological relationships.