Citations

Background: Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited disorder leading to kidney failure. Tolvaptan, the only FDA-approved therapy, modestly slows disease progression but is limited by significant adverse effects, highlighting the need for more effective and better-tolerated treatments. Ciliary polycystins are central to ADPKD pathogenesis. We previously demonstrated that a cilia base-localized pool of CDK6 restricts ciliary polycystin abundance by suppressing axonemal polyglutamylation. However, whether CDK6 inhibition can restore polycystin function and suppress ADPKD progression in vivo remains unknown. Methods: Abemaciclib was tested in in vitro 3D cyst assays and ex vivo metanephric organ cultures. In vivo efficacy of early- and late-stage intervention were assessed in F1(129/B6) Pkd1 R3277C/R3277C mice receiving daily abemaciclib. Tolvaptan served as a therapeutic control. Cyst burden, fibrosis in the kidneys, kidney function, and primary cilia of renal epithelial cells were analyzed at study endpoints. Results: CDK6 was prominently upregulated in cyst-lining cells in human and murine PKD kidneys. At doses substantially lower than those used in oncology, abemaciclib robustly suppressed cyst growth in vitro and ex vivo . In vivo , long-term early treatment arrested cyst progression more effectively than tolvaptan without detectable toxicity. Late intervention largely halted cyst growth in females and reversed cyst progression in males. Mechanistically, abemaciclib restored axonemal polyglutamylation and increased ciliary polycystin levels. Conclusions: Abemaciclib has greater therapeutic efficacy and tolerability than tolvaptan in this preclinical model, largely driven by CDK6 inhibition–mediated restoration of axonemal polyglutamylation and increased ciliary polycystin abundance.

Abstract Introduction: DRd is the standard of care for frontline (FL) treatment (tx) of transplant-ineligible (TIE) patients with newly diagnosed multiple myeloma (NDMM). This is supported by its superior efficacy and tolerable safety profile vs lenalidomide and dexamethasone (Rd) and vs bortezomib plus Rd (VRd) per the phase 3 MAIA clinical trial and real-world data. However, based on recent phase 3 CEPHEUS and IMROZ trial data, the tx paradigm is shifting toward the use of quadruplets for suitable TIE patients with NDMM. CEPHEUS demonstrated the superior efficacy of DVRd vs VRd in TIE and transplant-deferred patients with NDMM. DVRd-treated patients achieved significantly higher rates of minimal residual disease negativity and significantly improved progression-free survival vs VRd-treated patients. DVRd is listed as a National Comprehensive Cancer Network (NCCN) Category 1 preferred regimen in this setting and is therefore used in US real-world clinical practice. The objective of this study was to evaluate real-world usage patterns of FL DVRd and FL DRd in nontransplanted patients with NDMM and to assess the characteristics of patients treated with these regimens. Methods:Data from the Flatiron Health Research database were used for this retrospective observational study. Patients were included in this analysis if they received FL tx with DVRd or DRd for NDMM between Jan 1, 2019, and Dec 31, 2024. The index date was defined as the initiation date of FL DVRd or FL DRd. As the Flatiron database does not capture transplant eligibility status, the analysis excluded all patients who underwent hematopoietic stem cell transplantation at any time during the study period. Patients were also excluded if they were <18 years of age, enrolled in a clinical trial, had presence of other cancers, received chimeric antigen receptor T-cell therapy, or were diagnosed with amyloid light-chain amyloidosis before the index date. High cytogenetic risk was defined as the presence of abnormalities including del(17p), t(4;14), or t(14;16). Descriptive statistics were used to report demographic and clinical characteristics. Kaplan-Meier methods were used to estimate duration of therapy. Results: Among the nontransplanted NDMM cohort, 704 FL DVRd-treated patients and 396 FL DRd-treated patients were identified. At index, FL DVRd patients were generally younger than FL DRd patients (median age, 68 vs 78 years, respectively), more likely to be male (55.3% vs 49.5%), and less likely to have Medicare coverage (8.4% vs 17.2%). The 2 cohorts had similar proportions of Black/African American patients (18.9% and 18.7%). Among patients with available data, high cytogenetic risk was more frequently observed in FL DVRd (29.2%) vs FL DRd (17.5%) patients; a lower proportion of FL DVRd patients had International Staging System (ISS) stage III disease (27.1%) than ISS stage I disease (39.9%), whereas a higher proportion of FL DRd patients had ISS stage III disease (32.9%) than ISS stage I disease (25.5%). FL DVRd patients were more likely to be nonfrail (Intergroupe Francophone du Myélome simplified frailty score <2) vs FL DRd patients (64.6% vs 28.2%). Use of both DVRd and DRd increased during the study period; however, the increase was greater for DVRd, particularly in the later years. Notably, FL DVRd was started in 10 patients in 2019, increasing to 146 in 2022 and 222 in 2024. By comparison, FL DRd was initiated in 17 patients in 2019, increasing to 85 in 2022 and 97 in 2024. Median follow-up was 15.6 mo in the DVRd cohort and 20.3 mo in the DRd cohort. Median duration of DVRd therapy was 18.5 mo (95% CI, 14.8–22.7) and was 23.5 mo (95% CI, 19.0–31.7) for DRd therapy. Bortezomib as part of the DVRd regimen was given once weekly or less frequently in the majority (65.6%) of patients. Conclusions: These real-world data show the increasing FL use of the daratumumab-based quadruplet regimen DVRd among nontransplanted patients with NDMM. FL DVRd patients were generally younger and less frail but more likely to have high cytogenetic risk than those treated with DRd. These data also show that daratumumab-based regimens, either as a triplet (DRd) or a quadruplet (DVRd), are increasingly adopted over time in real-world clinical practice. These data further suggest that DRd and DVRd may be considered foundational for the tx of nontransplanted patients with NDMM regardless of patient characteristics, including age, frailty, cytogenetic risk, and ISS stage.

Key Points Inositol polyphosphate-5-phosphatase E (INPP5E) and type Ig phosphatidylinositol-4-phosphate 5-kinase (PIPKIγ) coordinated the homeostasis of phosphatidylinositol-4-phosphate and phosphatidylinositol-4,5-bisphosphate in primary cilia. Modulating INPP5E or PIPKIγ activity changed the level of polycystin-1 and polycystin-2 in primary cilia. INPP5E inhibition increased the hypomorphic PKD1 variants (PC1-R3277C) in cilia and reduced cystogenesis in the kidney in vitro . Background Autosomal dominant polycystic kidney disease is mainly caused by mutations in PKD1 and PKD2 , which encode polycystin-1 (PC1) and polycystin-2 (PC2), respectively. PC1 and PC2 assemble a cation channel complex enriched in primary cilium, a sensory organelle associated with various developmental diseases, including polycystic kidney disease (PKD). Accumulating evidence supports the necessity of functional polycystin (PC) complex in cilia to prevent cystogenesis in the kidney, indicating that improving their ciliary levels may ameliorate defects underlying PKD pathogenesis. Yet, molecular mechanisms underlying the ciliary targeting and homeostasis of the PC complex are not fully understood. Methods Indirect immunofluorescence microscopy was used to monitor ciliary levels of PC1 and PC2 in renal epithelial cells. Electrophysiology analysis in oocytes was used to determine the channel activity of the PC complex. Cystogenesis in the kidney was measured using in vitro 3D-Matrigel cell models and ex vivo mouse embryonic kidney models. Results Suppressing inositol polyphosphate-5-phosphatase E (INPP5E) or activating type Ig phosphatidylinositol-4-phosphate 5-kinase raised ciliary levels of the PC complex in both normal renal epithelial cells and cells carrying autosomal dominant polycystic kidney disease mutations that interrupt the trafficking of PCs into cilia, including GANAB inactivation and the trafficking PKD1 mutation p.Arg3277Cys (RC). PC1 RC formed a complex with PC2 and exhibited normal channel activity in vitro . An INPP5E that increases PC1 and PC2 in cilia, suppressed in vitro forskolin-induced cystogenesis of inner medullary collecting duct epithelial cell line 3 cells in 3D Matrigel and ex vivo cyst formation in embryonic Pkd1 RC/RC mouse kidneys. Conclusions Our results demonstrated that increasing the ciliary level of PCs, by manipulating a ciliary phosphoinositide signaling axis, enhanced the functionality of PCs and suppressed cystogenesis of renal epithelial cells in vitro .

Currently, the vasopressin V2 receptor antagonist tolvaptan is the only approved treatment for autosomal dominant polycystic kidney disease (ADPKD). It has been suggested that vasopressin acting on V1a or V1b receptors may also affect its development. We show that a V1aR antagonist has no effect in an ADPKD mouse model (Pkd1RC/RC), whereas a V2R antagonist has a modest attenuating effect in female mice only. Neither potentiates or hinders the beneficial effect of tolvaptan when administered in combination with this drug.

Tubulin polyglutamylation is a posttranslational modification that occurs primarily along the axoneme of cilia. Defective axoneme polyglutamylation impairs cilia function and has been correlated with ciliopathies, including Joubert Syndrome (JBTS). However, the precise mechanisms regulating proper axoneme polyglutamylation remain vague. Here, we show that cyclin-dependent kinase 6 (CDK6), but not its paralog CDK4, localizes to the cilia base and suppresses axoneme polyglutamylation by phosphorylating RAB11 family interacting protein 5 (FIP5) at site S641, a critical regulator of cilia import of glutamylases. S641 phosphorylation disrupts the ciliary recruitment of FIP5 and its association with RAB11, thereby reducing the ciliary import of glutamylases. Encouragingly, the FDA-approved CDK4/6 inhibitor Abemaciclib can effectively restore cilia function in JBTS cells with defective glutamylation. In summary, our study elucidates the regulatory mechanisms governing axoneme polyglutamylation and suggests that developing CDK6-specific inhibitors could be a promising therapeutic strategy to enhance cilia function in ciliopathy patients.

Heterotopic ossification (HO), defined as the formation of extraskeletal bone in muscle and soft tissues, is a diverse pathological process caused by either genetic mutations or inciting trauma. Fibrodysplasia ossificans progressiva (FOP) is a genetic form of HO caused by mutations in the bone morphogenetic protein (BMP) type I receptor gene activin A receptor type 1 ( ACVR1 ). These mutations make ACVR1 hypersensitive to BMP and responsive to activin A. Hedgehog (Hh) signaling also contributes to HO development. However, the exact pathophysiology of how skeletogenic cells contribute to endochondral ossification in FOP remains unknown. Here, we showed that the wild-type or FOP-mutant ACVR1 localized in the cilia of stem cells from human exfoliated deciduous teeth with key FOP signaling components, including activin A receptor type 2A/2B, SMAD family member 1/5, and FK506-binding protein 12kD. Cilia suppression by deletion of intraflagellar transport 88 or ADP ribosylation factor like GTPase 3 effectively inhibited pathological BMP and Hh signaling, subdued aberrant chondro-osteogenic differentiation in primary mouse or human FOP cells, and diminished in vivo extraskeletal ossification in Acvr1 Q207D , Sox2-Cre ; Acvr1 R206H/+ FOP mice and in burn tenotomy–treated wild-type mice. Our results provide a rationale for early and localized suppression of cilia in affected tissues after injury as a therapeutic strategy against either genetic or acquired HO.

AbstractServing as the cell's sensory antennae, primary cilia are linked to numerous human genetic diseases when they malfunction. DZIP1L, identified as one of the genetic causes of human autosomal recessive polycystic kidney disease (ARPKD), is an evolutionarily conserved ciliary basal body protein. Although it has been reported that DZIP1L is involved in the ciliary entry of PKD proteins, the underlying mechanism remains elusive. Here, an uncharacterized role of DZIP1L is reported in modulating the architecture and function of transition fibers (TFs), striking ciliary base structures essential for selective cilia gating. Using C. elegans as a model, C01G5.7 (hereafter termed DZIP‐1) is identified as the sole homolog of DZIP1L, which specifically localizes to TFs. While DZIP‐1 or ANKR‐26 (the ortholog of ANKRD26) deficiency shows subtle impact on TFs, co‐depletion of DZIP‐1 and ANKR‐26 disrupts TF assembly and cilia gating for soluble and membrane proteins, including the ortholog of ADPKD protein polycystin‐2. Notably, the synergistic role for DZIP1L and ANKRD26 in the formation and function of TFs is highly conserved in mammalian cilia. Hence, the findings illuminate an evolutionarily conserved role of DZIP1L in TFs architecture and function, highlighting TFs as a vital part of the ciliary gate implicated in ciliopathies ARPKD.