Anti-PD-L1-Based Bispecific Antibodies Targeting Co-Inhibitory and Co-Stimulatory Molecules for Cancer Immunotherapy.

Targeting PD-L1 via monospecific antibodies has shown durable clinical benefits and long-term remissions where patients exhibit no clinical cancer signs for many years after treatment. However, the durable clinical benefits and long-term remissions by anti-PD-L1 monotherapy have been limited to a small fraction of patients with certain cancer types. Targeting PD-L1 via bispecific antibodies (referred to as anti-PD-L1-based bsAbs) which can simultaneously bind to both co-inhibitory and co-stimulatory molecules may increase the durable antitumor responses in patients who would not benefit from PD-L1 monotherapy. A growing number of anti-PD-L1-based bsAbs have been developed to fight against this deadly disease. This review summarizes recent advances of anti-PD-L1-based bsAbs for cancer immunotherapy in patents and literatures, and discusses their anti-tumor efficacies in vitro and in vivo. Over 50 anti-PD-L1-based bsAbs targeting both co-inhibitory and co-stimulatory molecules have been investigated in biological testing or in clinical trials since 2017. At least eleven proteins, such as CTLA-4, LAG-3, PD-1, PD-L2, TIM-3, TIGIT, CD28, CD27, OX40, CD137, and ICOS, are involved in these investigations. Twenty-two anti-PD-L1-based bsAbs are being evaluated to treat various advanced cancers in clinical trials, wherein the indications include NSCLC, SNSCLC, SCLC, PDA, MBNHL, SCCHN, UC, EC, TNBC, CC, and some other malignancies. The released data from clinical trials indicated that most of the anti-PD-L1-based bsAbs were well-tolerated and showed promising antitumor efficacy in patients with advanced solid tumors. However, since the approved and investigational bsAbs have shown much more significant adverse reactions compared to PD-L1 monospecific antibodies, anti-PD-L1-based bsAbs may be further optimized via molecular structure modification to avoid or reduce these adverse reactions.

Design, synthesis and in vitro evaluation of amidoximes as histone deacetylase inhibitors for cancer therapy.

Amindoximes are geometric isomers of N-hydroxyamidines which are bioisosteres of hydroxamates. Since amindoxime group is capable of chelating transition metal ions including zinc ion, amindoximes should possess histone deacetylases (HDACs) inhibitory activity. In this work, we designed and synthesized a series of amindoximes, examined their inhibitory activities against HDACs, and investigated their cytotoxicity to human cancer cells. Preliminary results demonstrated that amindoximes possessed submicromolar HDACs inhibitory activity, with noteworthy enhancement compared with hydroxamates. Furthermore, the amindoximes arrested HCT116 and A549 cells in G2/M phase and showed good efficacy in inducing cells death. We provided a proof-of-concept that amindoximes could be used as HDACs inhibitors and hold great promise as epigenetic drugs.

Small molecules as antagonists of co-inhibitory pathways for cancer immunotherapy: a patent review (2018-2019).

INTRODUCTION: Therapeutic antibodies blocking co-inhibitory pathways do not attack tumor cells directly, but instead bind to their targeted proteins and mobilize the immune system to eradicate tumors. However, only a small fraction of patients with certain cancer types can benefit from the antibodies. Additionally, antibodies have shown serious immune-related adverse events in certain patients. Small-molecule antagonists may be a complementary and potentially synergistic approach to antibodies for patients with various cancers. AREAS COVERED: The authors review the small molecules as antagonists of co-inhibitory pathway proteins, summarize their preliminary SARs, discuss biochemistry assays used in patents for the development of small molecules as novel antagonists. EXPERT OPINION: The disclosed pharmacophores of small molecules as co-inhibitory pathway antagonists are represented by biphenyl derivatives, biaryl derivatives, teraryl derivatives, quateraryl derivatives, and oxadiazole/thiadiazole derivatives. However, these antagonists are still inferior to therapeutic antibodies in their inhibitory activities due to relatively flat of human co-inhibitory pathways proteins. Allosteric modulators may be an alternative approach. The more safety and efficacy evaluation trials of small-molecule antagonists targeting co-inhibitory pathways should be performed to demonstrate the proof-of-principle that small-molecule antagonists can result in sustained safety and antitumor response in the near future.

PD-1/PD-L1 Inhibitors for Immuno-oncology: From Antibodies to Small Molecules.

BACKGROUND: The recent regulatory approvals of immune checkpoint protein inhibitors, such as ipilimumab, pembrolizumab, nivolumab, atezolizumab, durvalumab, and avelumab ushered a new era in cancer therapy. These inhibitors do not attack tumor cells directly but instead mobilize the immune system to re-recognize and eradicate tumors, which endows them with unique advantages including durable clinical responses and substantial clinical benefits. PD-1/PD-L1 inhibitors, a pillar of immune checkpoint protein inhibitors, have demonstrated unprecedented clinical efficacy in more than 20 cancer types. Besides monoclonal antibodies, diverse PD- 1/PD-L1 inhibiting candidates, such as peptides, small molecules have formed a powerful collection of weapons to fight cancer. METHODS: The goal of this review is to summarize and discuss the current PD-1/PD-L1 inhibitors including candidates under clinical development, their molecular interactions with PD-1 or PD-L1, the disclosed structureactivity relationships of peptides and small molecules as inhibitors. RESULTS: Current PD-1/PD-L1 inhibitors under clinical development are exclusively dominated by antibodies. The molecular interactions of therapeutic antibodies with PD-1 or PD-L1 have been gradually elucidated for the design of novel inhibitors. Various peptides and traditional small molecules have been investigated in preclinical model to discover novel PD-1/PD-L1 inhibitors. CONCLUSION: Peptides and small molecules may play an important role in immuno-oncology because they may bind to multiple immune checkpoint proteins via rational design, opening opportunity for a new generation of novel PD-1/PD-L1 inhibitors.

Small Molecules as PD-1/PD-L1 Pathway Modulators for Cancer Immunotherapy.

Blockade of PD-1/PD-L1 interactions using PD-1/PD-L1 pathway modulators has shown unprecedented clinical efficacy in various cancer models. Current PD-1/PD-L1 modulators approved by FDA are exclusively dominated by therapeutic antibodies. Nevertheless, therapeutic antibodies also exhibit several disadvantages such as low tumor penetration, difficulty in crossing physiological barriers, lacking oral bioavailability, high manufacturing costs, inaccessible to intracellular targets, immunogenicity, immune-related adverse events (irAEs). Modulation of PD-1/PD-L1 pathway using small molecules may be an alternative approach to mobilize immune system to fight against cancers. In this review, we focus on summarizing the recently disclosed chemical structures and preliminary structure-activity relationships (SARs) of small molecules as PD-1/PD-L1 modulators for cancer immunotherapy.

Enhancing both CT imaging and natural killer cell-mediated cancer cell killing by a GD2-targeting nanoconstruct.

Although nanomaterials have been widely investigated for drug delivery, imaging and immunotherapy, their potential roles in triggering innate cellular immune responses while simultaneously serving as imaging enhancer remain unexplored. In this work, gold nanoparticles (GNPs) conjugated to the tumor-targeting anti-GD2 antibody hu14.18K322A, namely HGNPs, were designed and synthesized to specifically enhance computerized tomography (CT) imaging contrast and to stimulate the attack of neuroblastoma and melanoma cells by natural killer (NK) cells. The HGNPs specifically targeted GD2-positive neuroblastoma (NB1691) and melanoma (M21) cells, with an enhancement of CT contrast images of the HGNP-labeled cell pellets by 5.27- and 7.66-fold, respectively, compared to images of unlabeled cell pellets. The HGNPs also triggered NK-mediated antibody-dependent cellular cytotoxicity (ADCC) in NB1691 and M21 cells with a two-fold higher efficacy compared to that elicited by hu14.18K322A alone, with no adverse effect to GD2-negative PC-3 cells. These results suggest that HGNPs are promising theranostic agents for neuroblastoma and melanoma cancers.