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Despite its success in achieving the long-term survival of 10–30% of treated individuals, immune therapy is still ineffective for most patients with cancer 1 , 2 . Many efforts are therefore underway to identify new approaches that enhance such immune ‘checkpoint’ therapy 3 – 5 (so called because its aim is to block proteins that inhibit checkpoint signalling pathways in T cells, thereby freeing those immune cells to target cancer cells). Here we show that inhibiting PCSK9—a key protein in the regulation of cholesterol metabolism 6 – 8 —can boost the response of tumours to immune checkpoint therapy, through a mechanism that is independent of PCSK9’s cholesterol-regulating functions. Deleting the PCSK9 gene in mouse cancer cells substantially attenuates or prevents their growth in mice in a manner that depends on cytotoxic T cells. It also enhances the efficacy of immune therapy that is targeted at the checkpoint protein PD1. Furthermore, clinically approved PCSK9-neutralizing antibodies synergize with anti-PD1 therapy in suppressing tumour growth in mouse models of cancer. Inhibiting PCSK9—either through genetic deletion or using PCSK9 antibodies—increases the expression of major histocompatibility protein class I (MHC I) proteins on the tumour cell surface, promoting robust intratumoral infiltration of cytotoxic T cells. Mechanistically, we find that PCSK9 can disrupt the recycling of MHC I to the cell surface by associating with it physically and promoting its relocation and degradation in the lysosome. Together, these results suggest that inhibiting PCSK9 is a promising way to enhance immune checkpoint therapy for cancer. Inhibiting the PCSK9 protein, a regulator of cholesterol metabolism, enhances immune checkpoint therapy in mouse models of cancer, in a manner that depends on the regulation of antigen-presenting MHC I molecules.

In six trials comparing the anti–PCSK9 antibody bococizumab with placebo, the reduction in LDL cholesterol at 12 weeks was 55.2 percentage points lower with bococizumab. However, antidrug antibodies that developed in many patients reduced the magnitude of the reduction. Reducing levels of low-density lipoprotein (LDL) cholesterol with statin therapy is a highly effective method for reducing cardiovascular risk. 1 Trial data, observational studies, and genetic analyses indicate that further reductions in LDL cholesterol levels are likely to confer greater cardiovascular benefits. 2 – 4 Yet, recent studies have shown wide variability in the individual response of patients to statin therapy in terms of the percent reduction in LDL cholesterol levels. 5 , 6 Inhibitors of proprotein convertase subtilisin–kexin type 9 (PCSK9) reduce plasma LDL cholesterol levels by slowing PCSK9-mediated degradation of the LDL receptor. 7 Fully human monoclonal antibodies such as alirocumab and evolocumab that . . .

In two randomized trials comparing the PCSK9 inhibitor bococizumab with placebo, bococizumab had no benefit with respect to major adverse cardiovascular events in the lower-risk group but did have a significant benefit in the higher-risk group. Monoclonal antibodies that inhibit proprotein convertase subtilisin–kexin type 9 (PCSK9) lower levels of plasma low-density lipoprotein (LDL) cholesterol and are promising agents for vascular risk reduction. 1 Patients who have received the fully human monoclonal antibodies evolocumab and alirocumab, for example, have had reductions in cardiovascular events in preliminary analyses; these drugs are under evaluation in large-scale trials involving patients with known cardiovascular disease. 2 , 3 Bococizumab is a third inhibitor of PCSK9 that, unlike evolocumab and alirocumab, is a humanized monoclonal antibody in which approximately 3% of the murine sequence remains in the antigen-binding complementarity-determining region. As part of the Studies . . .

Genome editing using CRISPR-Cas systems is a promising avenue for the treatment of genetic diseases. However, cellular and humoral immunogenicity of genome editing tools, which originate from bacteria, complicates their clinical use. Here we report reduced immunogenicity (Red)(i)-variants of two clinically relevant nucleases, SaCas9 and AsCas12a. Through MHC-associated peptide proteomics (MAPPs) analysis, we identify putative immunogenic epitopes on each nuclease. Using computational modeling, we rationally design these proteins to evade the immune response. SaCas9 and AsCas12a Redi variants are substantially less recognized by adaptive immune components, including reduced binding affinity to MHC molecules and attenuated generation of cytotoxic T cell responses, yet maintain wild-type levels of activity and specificity. In vivo editing of PCSK9 with SaCas9.Redi.1 is comparable in efficiency to wild-type SaCas9, but significantly reduces undesired immune responses. This demonstrates the utility of this approach in engineering proteins to evade immune detection. CRISPR-mediated genome editing tools are entering the clinic, but concerns remain about the potential immunogenicity of these bacterial-derived proteins. Here, Raghavan et al. engineer two Cas effectors, Cas9 and Cas12, for reduced immunogenicity in vivo while maintaining on-target activity.

The cyclic GMP–AMP synthase (cGAS)–stimulator of interferon genes (STING) pathway is a central regulator of innate immunity and a promising target for cancer immunotherapy. However, the clinical translation of STING agonists is limited by suboptimal response rates and dose-limiting toxicities, particularly in the liver. These challenges highlight the presence of endogenous inhibitors of STING signaling and underscore the need for strategies that enable tissue-specific modulation of STING activity. Here, we identify proprotein convertase subtilisin/kexin type 9 (PCSK9), a key regulator of cholesterol metabolism, as a negative modulator of STING activation. Mechanistically, PCSK9 competes with STING for binding to a shared cargo receptor, which is critical for STING trafficking. PCSK9 deficiency markedly enhances the immunostimulatory effects of STING agonists. Capitalizing on the elevated expression of PCSK9 in the liver relative to tumors, we develop a formulation that delivers a low-dose STING agonist alongside PCSK9-targeting siRNA, thereby achieving tumor-selective STING activation while minimizing hepatotoxicity. These findings reveal an unanticipated role for PCSK9 in innate immune regulation and establish a therapeutic approach to enhance the safety and efficacy of STING-based immunotherapies, with broader implications for other STING-associated modalities, including radiotherapy and chemotherapy. The clinical translation of STING agonists is limited by suboptimal response rates and dose-limiting toxicities. Here, this group identifies a regulator of cholesterol metabolism as a negative modulator of STING activation, then develops a formulation delivering low-dose STING agonist alongside PCSK9-targeting siRNA for cancer therapy.

Nanobodies (Nbs) hold great potential to replace conventional antibodies in various biomedical applications. However, conventional methods for their discovery can be time-consuming and expensive. We have developed a reliable protein selection strategy that combines magnetic activated cell sorting (MACS)-based screening of yeast surface display (YSD) libraries and functional ligand-binding identification by Tat-based recognition of associating proteins (FLI-TRAP) to isolate antigen-specific Nbs from synthetic libraries. This combined process enabled isolation of three unique Nb clones (NbT15, NbT21, and NbT22) that all bound specifically to a target antigen, namely proprotein convertase subtilisin/kexin type 9 (PCSK9) as well as a gain-of-function PCSK9 mutant (D374Y). All three clones bound to PCSK9 and blocked the interaction between the low-density lipoprotein receptor (LDLR) and either wild-type PCSK9 or the D374Y mutant. Overall, our combined protein selection method enables rapid and straightforward identification of potent antigen-specific Nbs in a manner that can be executed in a basic laboratory setting without the need for specialized equipment. We anticipate that our strategy will be a valuable addition to the protein engineering toolkit, allowing development of Nbs or virtually any other synthetic binding protein for a wide range of applications.

Purpose Even with statins and other lipid-lowering therapy (LLT), many patients with heterozygous familial hypercholesterolemia (heFH) continue to have elevated low-density lipoprotein cholesterol (LDL-C) levels. ODYSSEY HIGH FH (NCT01617655) assessed the efficacy and safety of alirocumab, a proprotein convertase subtilisin/kexin type 9 monoclonal antibody, versus placebo in patients with heFH and LDL-C ≥ 160 mg/dl despite maximally tolerated statin ± other LLT. Methods Patients were randomized to subcutaneous alirocumab 150 mg or placebo every 2 weeks (Q2W) for 78 weeks. The primary endpoint was percent change in LDL-C from baseline to week 24. Results Mean baseline LDL-C levels were 196.3 mg/dl in the alirocumab ( n  = 71) and 201.0 mg/dl in the placebo groups ( n  = 35). Significant mean (standard error [SE]) reductions in LDL-C from baseline to week 24 were observed with alirocumab (−45.7 [3.5] %) versus placebo (−6.6 [4.9] %), a difference of −39.1 (6.0) % ( P  < 0.0001). Absolute mean (SE) LDL-C levels were reduced from baseline by 90.8 (6.7) mg/dl with alirocumab at week 24, with reductions maintained to week 78. Treatment-emergent adverse events were generally comparable between groups. Injection-site reactions were more frequent in the alirocumab group (8.3 %) versus placebo (5.7 %); most were mild in severity and did not result in study medication discontinuation. Conclusions In patients with heFH and very high LDL-C baseline levels despite maximally tolerated statin ± other LLT, alirocumab 150 mg Q2W demonstrated significant reductions in LDL-C levels with 41 % of patients achieving predefined LDL-C goals. Alirocumab was generally well tolerated.

PurposeAT04A and AT06A are two AFFITOPE® peptide vaccine candidates being developed for the treatment of hypercholesterolemia by inducing proprotein convertase subtilisin/kexin type 9 (PCSK9)-specific antibodies. This study aimed to investigate safety, tolerability, antibody development, and reduction of low-density lipoprotein cholesterol (LDLc) following four subcutaneous immunizations.MethodsThis phase I, single-blind, randomized, placebo-controlled study was conducted in a total of 72 healthy subjects with a mean fasting LDLc level at baseline of 117.1 mg/dL (range 77–196 mg/dL). Each cohort enrolled 24 subjects to receive three priming immunizations at weeks 0, 4, and 8 and to receive a single booster immunization at week 60 of either AT04A, AT06A, or placebo. In addition to safety (primary objective), the antigenic peptide- and PCSK9-specific antibody response and the impact on LDLc were evaluated over a period of 90 weeks.ResultsThe most common systemic treatment-related adverse events (AEs) reported were fatigue, headache, and myalgia in 75% of subjects in the AT06A group and 58% and 46% of subjects in the placebo and AT04A groups, respectively. Injection site reactions (ISR) representing 63% of all treatment-emergent adverse events (TEAEs), were transient and mostly of mild or moderate intensity and rarely severe (3%). Both active treatments triggered a robust, long-lasting antibody response towards the antigenic peptides used for immunization that optimally cross-reacted with the target epitope on PCSK9. In the AT04A group, a reduction in serum LDLc was observed with a mean peak reduction of 11.2% and 13.3% from baseline compared to placebo at week 20 and 70 respectively, and over the whole study period, the mean LDLc reduction for the AT04A group vs. placebo was −7.2% (95% CI [−10.4 to −3.9], P < 0.0001). In this group, PCSK9 target epitope titers above 50 were associated with clinically relevant LDLc reductions with an individual maximal decrease of 39%.ConclusionsAlthough both AT04A and AT06 were safe and immunogenic, only AT04A demonstrated significant LDLc-lowering activity, justifying further development.Trial registrationEudraCT: 2015-001719-11. ClinicalTrials.gov Identifier: NCT02508896.

Proprotein convertase subtilisin/kexin type 9 (PCSK9), a well-known regulator of cholesterol metabolism and cardiovascular diseases, has recently garnered attention for its emerging involvement in cancer biology. The multifunctional nature of PCSK9 extends beyond lipid regulation and encompasses a wide range of cellular processes that can influence cancer progression. Studies have revealed that PCSK9 can modulate signaling pathways, such as PI3K/Akt, MAPK, and Wnt/β-catenin, thereby influencing cellular proliferation, survival, and angiogenesis. Additionally, the interplay between PCSK9 and cholesterol homeostasis may impact membrane dynamics and cellular migration, further influencing tumor aggressiveness. The central role of the immune system in monitoring and controlling cancer is increasingly recognized. Recent research has demonstrated the ability of PCSK9 to modulate immune responses through interactions with immune cells and components of the tumor microenvironment. This includes effects on dendritic cell maturation, T cell activation, and cytokine production, suggesting a role in shaping antitumor immune responses. Moreover, the potential influence of PCSK9 on immune checkpoints such as PD1/PD-L1 lends an additional layer of complexity to its immunomodulatory functions. The growing interest in cancer immunotherapy has prompted exploration into the potential of targeting PCSK9 for therapeutic benefits. Preclinical studies have demonstrated synergistic effects between PCSK9 inhibitors and established immunotherapies, offering a novel avenue for combination treatments. The strategic manipulation of PCSK9 to enhance tumor immunity and improve therapeutic outcomes presents an exciting area for further investigations. Understanding the mechanisms by which PCSK9 influences cancer biology and immunity holds promise for the development of novel immunotherapeutic approaches. This review aims to provide a comprehensive analysis of the intricate connections between PCSK9, cancer pathogenesis, tumor immunity, and the potential implications for immunotherapeutic interventions.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) has emerged as a promising therapeutic target to reduce lipids. In 2020, we reported a chimeric camelid-human heavy chain antibody VHH-B11-Fc targeting PCSK9. Recently, it was verified that VHH-B11 binds one linear epitope in the PCSK9 hinge region. To enhance its druggability, we have developed a novel biparatopic B11-H2-Fc Ab herein. Thereinto, surface plasmon resonance (SPR) confirmed the epitope differences in binding-PCSK9 among VHH-B11, VHH-H2 and the approved Repatha. Additionally, SPR revealed the B11-H2-Fc exhibits an avidity of approximately 0.036 nM for PCSK9, representing a considerable increase compared to VHH-B11-Fc (~ 0.69 nM). Moreover, we found the Repatha and B11-H2-Fc exhibited > 95% PCSK9 inhibition efficiency compared to approximately 48% for the VHH-Fc at 7.4 nM ( P  < 0.0005). Further, we verified its biological activity using the human hepatoma cells G2 model, where the B11-H2-Fc exhibited almost 100% efficiency in PCSK9 inhibition at only 0.75 μM. The immunoblotting results of low-density lipoprotein cholesterol (LDL-c) uptake assay also demonstrated the excellent performance of B11-H2-Fc on recovering the LDL-c receptor (LDLR), as strong as the Repatha ( P  > 0.05). These findings provide the first evidence of the efficacy of a novel Ab targeting PCSK9 in the field of lipid-lowering drugs.