BYON4228 is a pan-allelic antagonistic SIRPα antibody that potentiates destruction of antibody-opsonized tumor cells and lacks binding to SIRPγ on T cells.

BACKGROUND: Preclinical studies have firmly established the CD47-signal-regulatory protein (SIRP)α axis as a myeloid immune checkpoint in cancer, and this is corroborated by available evidence from the first clinical studies with CD47 blockers. However, CD47 is ubiquitously expressed and mediates functional interactions with other ligands as well, and therefore targeting of the primarily myeloid cell-restricted inhibitory immunoreceptor SIRPα may represent a better strategy. METHOD: We generated BYON4228, a novel SIRPα-directed antibody. An extensive preclinical characterization was performed, including direct comparisons to previously reported anti-SIRPα antibodies. RESULTS: BYON4228 is an antibody directed against SIRPα that recognizes both allelic variants of SIRPα in the human population, thereby maximizing its potential clinical applicability. Notably, BYON4228 does not recognize the closely related T-cell expressed SIRPγ that mediates interactions with CD47 as well, which are known to be instrumental in T-cell extravasation and activation. BYON4228 binds to the N-terminal Ig-like domain of SIRPα and its epitope largely overlaps with the CD47-binding site. BYON4228 blocks binding of CD47 to SIRPα and inhibits signaling through the CD47-SIRPα axis. Functional studies show that BYON4228 potentiates macrophage-mediated and neutrophil-mediated killing of hematologic and solid cancer cells in vitro in the presence of a variety of tumor-targeting antibodies, including trastuzumab, rituximab, daratumumab and cetuximab. The silenced Fc region of BYON4228 precludes immune cell-mediated elimination of SIRPα-positive myeloid cells, implying anticipated preservation of myeloid immune effector cells in patients. The unique profile of BYON4228 clearly distinguishes it from previously reported antibodies representative of agents in clinical development, which either lack recognition of one of the two SIRPα polymorphic variants (HEFLB), or cross-react with SIRPγ and inhibit CD47-SIRPγ interactions (SIRPAB-11-K322A, 1H9), and/or have functional Fc regions thereby displaying myeloid cell depletion activity (SIRPAB-11-K322A). In vivo, BYON4228 increases the antitumor activity of rituximab in a B-cell Raji xenograft model in human SIRPαBIT transgenic mice. Finally, BYON4228 shows a favorable safety profile in cynomolgus monkeys. CONCLUSIONS: Collectively, this defines BYON4228 as a preclinically highly differentiating pan-allelic SIRPα antibody without T-cell SIRPγ recognition that promotes the destruction of antibody-opsonized cancer cells. Clinical studies are planned to start in 2023.

Discovery of SYD5115, a novel orally active small molecule TSH-R antagonist.

The thyrotropin receptor (TSH-R) regulates the thyroid gland and is normally activated by thyrotropin. In patients with Graves' disease, TSH-R is also stimulated by stimulatory TSH-R autoantibodies leading to hyperthyroidism. In this paper, we describe the discovery of SYD5115 (67), a novel small molecule TSH-R antagonist with nanomolar potency. SYD5115 also blocks stimulating antibody induced synthesis of the thyroid hormone thyroxine (T4) in vivo, after a single oral dose. During optimization, several issues had to be addressed such as the low metabolic stability and the potential mutagenicity of our first series of compounds.

A primary culture of distal convoluted tubules expressing functional thiazide-sensitive NaCl transport.

Studying the molecular regulation of the thiazide-sensitive Na(+)-Cl(-) cotransporter (NCC) is important for understanding how the kidney contributes to blood pressure regulation. Until now, a native mammalian cell model to investigate this transporter remained unknown. Our aim here is to establish, for the first time, a primary distal convoluted tubule (DCT) cell culture exhibiting transcellular thiazide-sensitive Na(+) transport. Because parvalbumin (PV) is primarily expressed in the DCT, where it colocalizes with NCC, kidneys from mice expressing enhanced green-fluorescent protein (eGFP) under the PV gene promoter (PV-eGFP-mice) were employed. The Complex Object Parametric Analyzer and Sorter (COPAS) was used to sort fluorescent PV-positive tubules from these kidneys, which were then seeded onto permeable supports. After 6 days, DCT cell monolayers developed transepithelial resistance values of 630 ± 33 Ω·cm(2). The monolayers also established opposing transcellular concentration gradients of Na(+) and K(+). Radioactive (22)Na(+) flux experiments showed a net apical-to-basolateral thiazide-sensitive Na(+) transport across the monolayers. Both hypotonic low-chloride medium and 1 µM angiotensin II increased this (22)Na(+) transport significantly by four times, which could be totally blocked by 100 µM hydrochlorothiazide. Angiotensin II-stimulated (22)Na(+) transport was also inhibited by 1 µM losartan. Furthermore, NCC present in the DCT monolayers was detected by immunoblot and immunocytochemistry studies. In conclusion, a murine primary DCT culture was established which expresses functional thiazide-sensitive Na(+)-Cl(-) transport.

NDUFA10 mutations cause complex I deficiency in a patient with Leigh disease.

Mitochondrial complex I deficiency is the most common defect of the oxidative phosphorylation system. We report a patient with Leigh syndrome who showed a complex I deficiency expressed in cultured fibroblasts and muscle tissue. To find the genetic cause of the complex I deficiency, we screened the mitochondrial DNA and the nuclear-encoded subunits of complex I. We identified compound-heterozygous mutations in the NDUFA10 gene, encoding an accessory subunit of complex I. The first mutation disrupted the start codon and the second mutation resulted in an amino acid substitution. The fibroblasts of the patient displayed decreased amount and activity, and a disturbed assembly of complex I. These results indicate that NDUFA10 is a novel candidate gene to screen for disease-causing mutations in patients with complex I deficiency.