Additive efficacy of a bispecific anti-TNF/IL-6 nanobody compound in translational models of rheumatoid arthritis

Rheumatoid arthritis (RA) is one of the most common autoimmune diseases affecting primarily the joints. Despite successful therapies including antibodies against tumor necrosis factor (TNF) and interleukin-6 (IL-6) receptor, only 20 to 30% of patients experience remission. We studied whether inhibiting both TNF and IL-6 would result in improved efficacy. Using backtranslation from single-cell RNA sequencing (scRNA-seq) data from individuals with RA, we hypothesized that TNF and IL-6 act synergistically on fibroblast-like synoviocytes (FLS) and T cells. Coculture of FLS from individuals with RA and T cells supported this hypothesis, revealing effects on both disease-driving pathways and biomarkers. Combining anti-TNF and anti-IL-6 antibodies in collagen-induced arthritis (CIA) mouse models resulted in sustained long-term remission, improved histology, and effects on bone remodeling pathways. These promising data initiated the development of an anti-TNF/IL-6 bispecific nanobody compound 1, with similar potencies against TNF and IL-6. We observed additive efficacy of compound 1 in a FLS/T cell coculture affecting arthritis and T helper 17 (T_H17) pathways. This nanobody compound transcript signature inversely overlapped with described RA endotypes, indicating a potential efficacy in a broader patient population. In summary, we showed superiority of a bispecific anti-TNF/IL-6 nanobody compound or combination treatment over monospecific treatments in both in vitro and in vivo models. We anticipate improved efficacy in upcoming clinical studies.

Rational Design of Highly Potent, Selective, and Bioavailable SGK1 Protein Kinase Inhibitors for the Treatment of Osteoarthritis

The serine/threonine kinase SGK1 is an activator of the β-catenin pathway and a powerful stimulator of cartilage degradation that is found to be upregulated under genomic control in diseased osteoarthritic cartilage. Today, no oral disease-modifying treatments are available and chronic treatment in this indication sets high requirements for the drug selectivity, pharmacokinetic, and safety profile. We describe the identification of a highly selective druglike 1H-pyrazolo[3,4-d]pyrimidine SGK1 inhibitor 17a that matches both safety and pharmacokinetic requirements for oral dosing. Rational compound design was facilitated by a novel hSGK1 co-crystal structure, and multiple ligand-based computer models were applied to guide the chemical optimization of the compound ADMET and selectivity profiles. Compounds were selected for subchronic proof of mechanism studies in the mouse femoral head cartilage explant model, and compound 17a emerged as a druglike SGK1 inhibitor, with a highly optimized profile suitable for oral dosing as a novel, potentially disease-modifying agent for osteoarthritis.

In vivo visualization of osteoarthritic hypertrophic lesions

Osteoarthritis (OA) is one of the most common diseases in the aging population. While disease progress in humans is monitored indirectly by X-ray or MRI, small animal OA lesions detection always requires surgical intervention and histology. Here we introduce bimodal MR/NIR probes based on cartilage-targeting 1,4,7,10-tetraazacyclododecane 1,4,7,10-tetraacetic acid amide (DOTAM) that are directly administered to the joint cavity. We demonstrate applications in healthy and diseased rat joints by MRI in vivo. The same joints are inspected post-mortem by fluorescence microscopy, showing not only the precise location of the reagents but also revealing details such as focal cartilage damage and chondrophyte or osteophyte formation. This allows for determining the distinct pathological state of the disease and the regeneration capability of the animal model and will help to correctly assess the effect of potential disease modifying OA drugs (DMOADs) in the future.

Correlational analysis for identifying genes whose regulation contributes to chronic neuropathic pain

BACKGROUND

Nerve injury-triggered hyperexcitability in primary sensory neurons is considered a major source of chronic neuropathic pain. The hyperexcitability, in turn, is thought to be related to transcriptional switching in afferent cell somata. Analysis using expression microarrays has revealed that many genes are regulated in the dorsal root ganglion (DRG) following axotomy. But which contribute to pain phenotype versus other nerve injury-evoked processes such as nerve regeneration? Using the L5 spinal nerve ligation model of neuropathy we examined differential changes in gene expression in the L5 (and L4) DRGs in five mouse strains with contrasting susceptibility to neuropathic pain. We sought genes for which the degree of regulation correlates with strain-specific pain phenotype.

RESULTS

In an initial experiment six candidate genes previously identified as important in pain physiology were selected for in situ hybridization to DRG sections. Among these, regulation of the Na+ channel alpha subunit Scn11a correlated with levels of spontaneous pain behavior, and regulation of the cool receptor Trpm8 correlated with heat hypersensibility. In a larger scale experiment, mRNA extracted from individual mouse DRGs was processed on Affymetrix whole-genome expression microarrays. Overall, 2552 +/- 477 transcripts were significantly regulated in the axotomized L5DRG 3 days postoperatively. However, in only a small fraction of these was the degree of regulation correlated with pain behavior across strains. Very few genes in the "uninjured" L4DRG showed altered expression (24 +/- 28).

CONCLUSION

Correlational analysis based on in situ hybridization provided evidence that differential regulation of Scn11a and Trpm8 contributes to across-strain variability in pain phenotype. This does not, of course, constitute evidence that the others are unrelated to pain. Correlational analysis based on microarray data yielded a larger "look-up table" of genes whose regulation likely contributes to pain variability. While this list is enriched in genes of potential importance for pain physiology, and is relatively free of the bias inherent in the candidate gene approach, additional steps are required to clarify which transcripts on the list are in fact of functional importance.

Stimulation of PAR-2 excites and sensitizes rat cutaneous C-nociceptors to heat

Proteinase-activated receptor 2 (PAR-2) is expressed on many nociceptive neurons. Application of PAR-2 agonists has been shown to induce behavioral signs of hyperalgesia. We investigated effects of the rat PAR-2 agonist SLIGRL-NH2 in the isolated rat skin-saphenous nerve preparation. SLIGRL-NH2 (100 microM) excited 20% of all C-fiber nociceptors tested. In addition, C-fiber nociceptors were sensitized to heat after SLIGRL-NH2 application resulting in an increase in response magnitude and a decrease of heat threshold. The PAR-2-inactive control peptide LRGILS-NH2 had no effect. The mechanical sensitivity of C-fibers was not affected by SLIGRL-NH2. PAR-2-mediated excitation and sensitization of primary nociceptors may contribute to PAR-2-mediated hyperalgesia.

Hair cell loss and regeneration after severe acoustic overstimulation in the adult pigeon

The extent of hair cell regeneration following acoustic overstimulation severe enough to destroy tall hair cells, was determined in adult pigeons. BrdU (5-bromo-2'-deoxyuridine) was used as a proliferation marker. Recovery of hearing thresholds in each individual animal was measured over a period of up to 16 weeks after trauma. In ears with loss of both short and tall hair cells, little or no functional recovery occurred. In ears with less damage, where significant functional recovery did occur, there were always a few rows of surviving hair cells left at the neural edge of the basilar papilla. In the region of hair cell loss, numerous BrdU labeled cells were found. However, only a small minority of these cells were regenerated hair cells, the majority being monolayer cells. Irrespective of the extent of the region of hair cell loss, regenerated hair cells were observed predominantly in a narrow strip at the transition from the abneural area of total hair cell loss and the neural area of hair cell survival. With increasing damage this strip moved progressively towards the neural edge of the papilla. No regeneration of hair cells was observed in the abneural region of total hair cell loss, even up to 16 weeks after trauma. The results indicate that there is a gradient in the destructive effect of loud sound across the width of the basilar papilla, from most detrimental at the abneural edge to least detrimental at the neural edge. Both tall and short hair cells can regenerate after sound trauma. Whether they do regenerate or not depends on the degree of damage to the area of the papilla where they normally reside. Regeneration of new hair cells occurs only in a narrow longitudinal band, which moves from abneural into the neural direction with increasing damage. In the area neural to this band, hair cells survive the overstimulation. In the area abneural to this band, sound damage is so severe, that no regeneration of hair cells occurs. As a consequence morphological and functional deficits persist.

Discharge properties of pigeon single auditory nerve fibers after recovery from severe acoustic trauma

The time course of recovery of compound action potential (CAP) thresholds was observed in individual adult pigeons after severe acoustic trauma. Each bird had electrodes implanted on the round window of both ears. One ear was exposed to a tone of 0.7 kHz at 136-142 dB SPL for 1 hr under general anesthesia. Recovery of CAP audiograms was monitored twice a week after trauma. Single unit recordings from auditory nerve fibers were made after 3 weeks and after 4 or more months of the exposure. The CAP was abolished immediately after overstimulation in all animals. Based on the temporal patterns of functional recovery of the CAP three groups of animals were identified. The first group was characterized by fast functional recovery starting immediately after trauma followed by a return to pre-exposure values within 3 weeks. In the second group, slow functional recovery of threshold started 1-2 weeks after trauma followed by a return to pre-exposure values by 4-5 weeks. A mean residual hearing loss of 26.3 dB at 2 kHz remained. The third group consisted of animals that did not recover after trauma. Three weeks after the exposure, tuning curves of single auditory nerve fibers were very broad and sometimes irregular in shape. Their thresholds hovered around 120 dB SPL. Spontaneous firing rate and driven rate were much reduced. Four or more months after exposure, the thresholds and sharpness of tuning of many single units were almost completely recovered. Spontaneous firing rate and driven rate were comparable to those of control animals. In the slow recovery group neuronal tuning properties showed less recovery, especially at frequencies above the exposure frequency. Thresholds and sharpness of tuning were normal at frequencies below the exposure frequency, but were much poorer at frequencies above the exposure. Spontaneous firing rate was much reduced in fibers with high characteristic frequencies. In fast recovering animals, the papilla was repopulated with hair cells after 4 months. In slow recovering animals, short (abneural) hair cells were still missing over large parts of the papilla after 4 months of recovery. Residual short (abneural) hair cell loss was largest at two areas, one more basal and the other more apical to the characteristic place of the traumatizing frequency. The results show that, in adult birds, functional recovery from severe damage to both short (abneural) and tall (neural) hair cells occurs. However, the onset of recovery is delayed and the time course is slower than after destruction of short (abneural) hair cells alone. Also, recovery is incomplete, both functionally and morphologically. There is residual permanent hearing loss, and regeneration of short (abneural) hair cells is incomplete.

Regeneration after tall hair cell damage following severe acoustic trauma in adult pigeons: correlation between cochlear morphology, compound action potential responses and single fiber properties in single animals

The time course of recovery of compound action potential (CAP) thresholds was observed in individual adult pigeons after severe acoustic trauma. Pigeons were overstimulated with a tone of 0.7 kHz and 136-142 dB SPL presented to one ear for 1 h under general anesthesia. Recovery of CAP audiograms was monitored at regular intervals after trauma. A new semi-stereotaxic approach to the peripheral part of the auditory nerve was developed. This permitted activity from single auditory nerve fibers to be recorded over a wide range of characteristic frequencies (CFs), including high CFs, without having to open the inner ear. Single unit recordings were made after three weeks and after 4 or more months of recovery. The time course of recovery, the single unit properties, and the morphological status of the basilar papilla were correlated. The CAP was abolished in all animals after overstimulation. Three groups of animals were identified according to the functional recovery of the CAP thresholds recorded at regular intervals with implanted electrodes: Group 1: Fast functional recovery starting immediately after trauma, followed by recovery to pre-exposure values within 3 weeks. Group 2: Slow functional recovery of threshold starting 1-2 weeks after trauma and ending 4-5 weeks after trauma. A mean residual hearing loss of 26.3 dB at 2 kHz remained. Group 3: No recovery of CAP thresholds up to 8 months after trauma. Three weeks after trauma, very few responsive neurons were found in groups 2 and 3. Tuning curves were very broad and sometimes irregular in shape. Thresholds were very high, around 120 dB SPL. Spontaneous firing rate was much reduced, especially in neurons with high CFs. After 4 or more months of recovery, the response properties of single units in group 1 had only partially recovered. Thresholds and sharpness of tuning of many single units were normal: however, in general they were still poorer than in control animals. Spontaneous firing rate was comparable to control animals. Neurons from animals in group 2 showed less recovery, especially at frequencies above the exposure frequency. Thresholds and sharpness of tuning were normal at frequencies below the exposure frequency, but were much poorer at frequencies above the exposure. Spontaneous firing rate was much reduced in fibers with high CFs. The basilar papilla in animals without recovery showed total loss of the sensory epithelium. The basal lamina of the basilar membrane, however, remained intact and was covered with cuboidal cells. In fast recovering animals, the papilla was repopulated with hair cells after 4 months. In slow recovering animals, short (abneural) hair cells were still missing over large parts of the papilla after 4 months of recovery. Residual short (abneural) hair cell loss was largest at two areas, one more basal and the other more apical to the characteristic place of the traumatizing frequency. The results show that functional recovery from severe damage to both short (abneural) and tall (neural) hair cells occurs in adult birds. However, the onset of recovery is delayed and the time course is slower than after destruction of short (abneural) hair cells alone. Furthermore recovery is incomplete, both functionally and morphologically. There are residual permanent hearing losses and regeneration of short (abneural) hair cells is incomplete.

A functional map of the pigeon basilar papilla: correlation of the properties of single auditory nerve fibres and their peripheral origin

The purpose of the investigation was to correlate the functional properties of primary auditory fibres with the location of appertaining receptor cells in the avian basilar papilla. The functional properties of 425 single afferent fibres from the auditory nerve of adult pigeons were measured. The peripheral innervation site of 39 fibres was identified by intracellular labelling and correlated with the fibre's functional properties. Mean spontaneous firing rate (SR, 0.1-250/s) was distributed monomodally (mean: 91 +/- 47/s) but not normally. Characteristic frequencies (CFs) were in the range of 0.02-4 kHz. SR, threshold at CF (4-76 dB SPL) and sharpness of tuning (Q10 dB, 0.1-8.8) varied systematically with CF. For a given CF there was a strong correlation of threshold and Q10 dB and of threshold and SR. Labelled fibres innervated different hair cell types over 93% of the length and 97% of the width of the basilar papilla. The majority of fibres innervated hair cells located between 30 and 70% distance from the apex and 0 and 30% distance from the neural edge of the papilla. CFs are mapped tonotopically from high at the base to low at the apex of the papilla, with a mean mapping constant of 0.63 +/- 0.05 mm/octave (in vivo). The highest CF at the base extrapolates to 5.98 +/- 1.17 kHz. The lowest CF mapped at the apex is 0.021 kHz. From the data, together with data from mechanical measurements (Gummer et al., 1987), a frequency-place function of the pigeon papilla was calculated. Transverse gradients of threshold at CF and of Q10 dB were observed across the width of the papilla. Thresholds were lowest and sharpness of tuning was highest above the neural limbus at a distance of 23% from the neural edge of the papilla. Hair cells in this sensitive strip are the tallest and narrowest ones across the width of the papilla. They are packed most densely and receive the largest number of afferent fibres. Fibres innervating (mostly short) hair cells on the free basilar membrane were spontaneously active and responsive to sound. Their Q10 dB was less than average but their sensitivity and SR were comparable to the mean population values. It is concluded that functional properties change gradually not only along the length but also across the width of the pigeon basilar papilla. The results support the idea that sharp frequency tuning of avian primary auditory fibres involves tuning mechanisms supplementary to the tuning of the free part of the basilar membrane.