Peptide-drug Conjugates Research Articles

Melflufen: A Peptide-Drug Conjugate for the Treatment of Multiple Myeloma.

Despite the availability of new therapies that have led to improved outcomes for patients with multiple myeloma, most patients will eventually relapse. With triplet and even quadruplet combination therapies becoming standard in the first and second line, many patients will have few treatment options after second-line treatment. Melflufen (melphalan flufenamide) is a first-in-class peptide–drug conjugate (PDC) that targets aminopeptidases and rapidly releases alkylating agents into tumor cells. Once inside the tumor cells, melflufen is hydrolyzed by peptidases to release alkylator molecules, which become entrapped. Melflufen showed anti-myeloma activity in myeloma cells that were resistant to bortezomib and the alkylator melphalan. In early phase studies (O-12-M1 and HORIZON [OP-106]), melflufen plus dexamethasone has demonstrated encouraging clinical activity and a manageable safety profile in heavily pretreated patients with relapsed/refractory multiple myeloma, including those with triple-class refractory disease and extramedullary disease. The Phase III OCEAN study (OP-104) is further evaluating melflufen plus dexamethasone in patients with relapsed/refractory multiple myeloma. The safety profile of melflufen is characterized primarily by clinically manageable hematologic adverse events. Melflufen, with its novel mechanism of action, has the potential to provide clinically meaningful benefits to patients with relapsed/refractory multiple myeloma, including those with high unmet needs.

Delivery of ionizable hydrophilic drugs based on pharmaceutical formulation of ion pairs and ionic liquids

New therapeutics such as antisense oligonucleotides, small interfering RNA and peptide-drug conjugates are taking great relevance in the pharmaceutical industry due to their specificity of action and their improved safety profile. However, they could present bioavailability issues due to their hydrophilic nature, such as BCS class III drugs. Therefore, the formation of ion pairs of these type of molecules allows modifying their physicochemical characteristics such as polarity and lipophilicity leading to improved permeability. By carrying out a tailored synthesis, it is possible to obtain complexes with greater stability and better performance in vitro and in vivo, where their correlation with physicochemical properties continues to be a growing field of research. Moreover, ionic liquids (IL), which are substances that melt below 100 °C, have enabled modifying various drug properties, showing promising results in vitro-in vivo, especially when they are included in suitable drug delivery systems, such as nanoparticles, microparticles, self-emulsifying drug delivery systems, and transdermal patches, among others. The drug-IL is formed from the therapeutic agent and a counterion, mainly by ionic interactions, and resulting in a wide variety of derivatives with different properties. However, the pharmaceutical field is limited to the use of some excipients or GRAS (generally recognized as safe) substances, so the search for new counterions is of great interest. In this article, we have compiled key indexes that can be obtained from databases to guide the search for suitable counterions, together with different drug delivery system strategies to choose the most appropriate formulation according to the non-parenteral route of administration selected. Intellectual property advancements in the field are also presented and analyzed.

Enhanced cancer treatment by an acid-sensitive cytotoxic peptide-doxorubicin conjugate

Peptide-drug conjugates (PDCs) prepared by covalent attachment of specific peptides to a chemotherapeutic drug are receiving great attention for their significantly improved antitumor effects. Due to the unique properties of the tumor microenvironment, stimulus-responsive PDCs represent a promising strategy for improving the treatment of many types of cancers. In this study, we developed an acid-sensitive cytotoxic peptide-doxorubicin conjugate by linking doxorubicin (Dox) with a proapoptotic peptide (KLAK) via a hydrazone linker. The KLAK-Dox conjugate showed acid-sensitive release characteristics, while it was stable in neutral buffer. KLAK-Dox showed relatively lower uptake than free Dox but exhibited remarkably enhanced cytotoxicity toward HeLa cells. Moreover, drug distribution analysis indicated that tumor accumulation of KLAK-Dox was 3-fold higher than that of free Dox in a cervical carcinoma xenograft model. The conjugate also demonstrated remarkably improved antitumor efficacy in mice bearing cervical carcinoma xenografts. Our results suggested that cytotoxic peptide-doxorubicin conjugates may represent potential anticancer drugs for future cancer treatment.

Shuttling of Peptide‐Drug Conjugates by G Protein‐Coupled Receptors Is Significantly Improved by Pulsed Application

G protein‐coupled receptors (GPCRs) can be used to shuttle peptide‐drug conjugates into cells. But, for efficient therapy, a high concentration of cargo needs to be delivered. To explore this, we studied the pharmacologically interesting neuropeptide Y1 receptor (Y1R) in one recombinant and three oncogenic cell systems that endogenously express the receptor. We demonstrate that recycled receptors behave identically to newly synthesized receptors with respect to ligand binding and internalization pathways. Depending on the cell system, biosynthesis, recycling efficiency, and peptide uptake differ partially, but shuttling was efficient in all systems. However, by comparing continuous application of the ligand for four hours to four cycles of internalization and recycling in between, a significantly higher amount of peptide uptake was achieved in the pulsed application (150–250 % to 300–400 %). Accordingly, in this well‐suited drug shuttle system pulsed application is superior under all investigated conditions and should be considered for innovative, targeted drug delivery in general.

MM-133: HORIZON (OP-106): Melflufen Plus Dexamethasone in Relapsed/Refractory Multiple Myeloma (RRMM) Refractory to Pomalidomide and/or an Anti-CD38 Monoclonal Antibody (mAb) – Final Primary Analysis

Context: Outcomes in RRMM remain poor (Kumar et al. Leukemia. 2017; 31:2443), and treatment options are limited for RRMM refractory to multiple drug classes (Gandhi et al. Leukemia. 2019; 33:2266). Melphalan flufenamide (melflufen) is a first-in-class anticancer peptide-drug conjugate that rapidly delivers an alkylating payload into tumor cells. A phase 1/2 study established the dosage of melflufen plus dexamethasone in RRMM (Richardson et al. Lancet Haematol. 2020; 7:e395). Objective: Evaluate the efficacy and safety of melflufen plus dexamethasone in RRMM in the pivotal, single-arm, multicenter, phase 2 HORIZON study ( NCT02963493 ). Methods: Patients who had RRMM, ≥2 prior lines of therapy (≥1 IMiD + ≥1 proteasome inhibitor [PI]), and were refractory to pomalidomide and/or an anti-CD38 mAb received melflufen plus dexamethasone until progressive disease or unacceptable toxicity. Primary endpoint: overall response rate (ORR; investigator-assessed per IMWG criteria). Secondary endpoints: duration of response (DOR), progression-free survival (PFS), overall survival (OS), and safety. Subgroup analyses: triple-class–refractory (TCR) disease (refractory to or intolerant of ≥1 IMiD + ≥1 PI + ≥1 anti-CD38 mAb) and extramedullary disease (EMD). Results: Of 157 patients treated (intention-to-treat [ITT]); 26 remain on study (data cutoff: January 14, 2020). Median age: 65 years (range, 35-86); 25% had ISS stage III disease; and 35% had EMD. Median prior lines of therapy: 5 (range, 2-12); 76% had TCR disease. In the ITT, ORR was 29% (95% CI, 22-37); median (95% CI) DOR was 5.5 months (3.9-7.6); PFS was 4.2 months (3.4-4.9); and OS was 11.6 months (9.3-15.4). In patients with TCR disease and EMD, ORR was 26% (95% CI, 18-35) and 24% (95% CI, 13-37), respectively; DOR, PFS, and OS will be presented. Most common grade 3/4 adverse events (AEs): neutropenia (79%), thrombocytopenia (76%), and anemia (43%). Most common nonhematologic grade 3/4 AEs: pneumonia (10%) and hypophosphatemia (5%). AEs led to melflufen dose reduction and discontinuation in 27% and 22% of patients, respectively. Most common serious AEs were pneumonia (9%) and febrile neutropenia (5%). No treatment-related deaths. Conclusion: Melflufen plus dexamethasone showed clinically meaningful efficacy with a manageable safety profile in heavily pretreated RRMM, including in patients with TCR disease and EMD.

Abstract 190: Prognostic significance of esterase gene expression in multiple myeloma

Abstract Introduction: The esterase enzyme family is a subclass of the hydrolase enzyme superfamily that functions to split ester bonds. Several esterases have been identified, which differ in substrate specificity and biological function, and the expression of specific esterases may be dysregulated in cancer. Limited information is available regarding the expression of esterases in multiple myeloma (MM), despite potential for exploitation in novel therapeutic approaches such as peptide-drug conjugates (e.g. melflufen). We evaluated the biological significance of esterase enzyme expression in MM. Methods: For gene expression profiling, bone marrow aspirates were obtained from MM patients (pts) or healthy donors after obtaining written informed consent and following approved protocols in compliance with the Declaration of Helsinki. CD138+ plasma cells were enriched and used for RNA preparation. Illumina-compatible RNA sequencing libraries were prepared and sequenced. A cut-off value of >1 Reads Per Kilobase of transcript per Million mapped reads (RPKM) was used to filter expressed genes. The Welch two-sample t-test was used to identify significant variation in gene expression. Contribution of esterase gene expression to survival outcome was estimated by Kaplan-Meier analysis; significance between two groups was deduced using a Mantel-Cox log rank test. Results: Of 123 pts with MM, bone marrow aspirates were collected from 41 pts with newly diagnosed (ND) MM, 81 pts with relapsed/refractory (RR) MM, and 1 pt with stable disease. Samples were also obtained from two healthy donors. The most abundant esterases in MM samples were OVCA2, PAFAH1B2, NXPE3, UCHL3, LIPA, ABHD10, UCHL5, CASD1, ABHD13, and USP4 (median log2[RPKM] range: 3.9 to 2.1). The least abundant esterases were NLGN1, NLGN2, PON1, CEL, PON3, NLGN4Y, IL17A, AADAC, CES5A, and ASPG (median log2[RPKM]: -5.1 to -10.7). The expression levels of OVCA2, PAFAH1B2, NXPE3, UCHL5, SIAE, ESD, PNPLA6, and PAFAH1B3 were significantly higher (P<0.05), and of PCED1B significantly lower (P<0.05), in RRMM versus NDMM. The expression level of all these genes was comparatively higher in the two healthy donor samples. High expression of OVCA2, PAFAH1B3, CES4A, or PNPLA6 was associated with poorer prognosis (overall survival [OS]) versus low expression samples (median OS for high vs low expression [months]: OVCA2: 55 vs 122; PAFAH1B3: 55 vs 124; CES4A: 55 vs not reached; PNPLA6: 89 vs 127; all P≤0.01), whereas low expression of NXPE4 or GZMA was associated with poorer prognosis versus high expression samples (median OS for high vs low expression [months]: NXPE4: 120 vs 55; GZMA: 120 vs 74; both P≤0.03). Conclusion: Esterase expression levels in MM change on progression from NDMM to RRMM. High expression of OVCA2, PAFAH1B3, CES4A, and PNPLA6, and low expression of NXPE4 and GZMA, were identified as poor prognostic markers in pts with MM, suggesting a role for these esterases in myeloma biology. Citation Format: Romika Kumari, M. Mamun Majumder, Juha Lievonen, Raija Silvennoinen, Pekka Anttila, Nina N. Nupponen, Fredrik Lehmann, Caroline A. Heckman. Prognostic significance of esterase gene expression in multiple myeloma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 190.

Abstract 685: Sortilin receptor-mediated novel cancer therapy: A targeted approach to inhibit vasculogenic mimicry in ovarian and breast cancers

Abstract Rational: Vasculogenic mimicry (VM) is defined as the formation of microvascular channels by aggressive, metastatic and genetically deregulated tumor cells. This microcirculation system, independent of endothelial cells, provides oxygen and nutrients to tumor cells. Such system contributes, in part, to current chemoresistance and facilitates tumor progression as well as dissemination of cancer metastases. VM is a process associated with aggressive ovarian cancer and triple-negative breast cancer (TNBC) and is shown to correlate with decreased overall cancer patient survival. Procedures: Targeting VM in ovarian and TNBC tumors, in addition to targeting tumor cells, may thus help circumvent chemoresistance and contribute to more efficient cancer treatments. Sortilin receptor (SORT1) is essential for VM in ovarian and TNBC tumors and high expression of SORT1 in many types of cancers has been associated with their invasion and progression. Results: SORT1 was detected in 3D-tubular structures of ES-2 ovarian cancer and MDA-MB-231 TNBC cells when grown on Matrigel. Peptide-drug conjugates targeting SORT1 significantly decreased the formation of new 3D-structures by 50% (IC50) at low nM concentrations (5-10 nM). In fact, the Doxorubicin-peptide conjugate (TH1904) abolished the formation of 3D-tubular structures of ovarian cancer cells in an in vitro model, whereas unconjugated Doxorubicin or liposomal Doxorubicin (up to 20 µM) had no effect on the formation of the VM structure. Moreover, a Docetaxel-peptide conjugate (TH1902) also showed very potent in vitro activity against the formation of VM in TNBC. IC50 values for VM 3D-tubular structures inhibition was about 30 pM for TH1902 compared to 0.5 nM for Docetaxel. Conclusion: Our results provide insight into future potent ovarian and TNBC therapeutic treatments. Targeting this receptor's functions with peptide-drug conjugates may provide an efficient strategy to increase the binding/internalization of cancer drugs within tumor cells, thereby improving the efficacy of standard anticancer treatments. Our results indicate that peptide-drug conjugates targeting SORT1 strongly inhibit the formation of VM, a phenomenon associated with a more aggressive tumor phenotype and poor prognosis in patients with TNBC or ovarian cancer. Citation Format: Jean-Christophe Currie, Michel Demeule, Alain Larocque, Alain Zgheib, Richard Béliveau, Christian Marsolais, Borhane Annabi. Sortilin receptor-mediated novel cancer therapy: A targeted approach to inhibit vasculogenic mimicry in ovarian and breast cancers [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 685.

Abstract 6272: Redirecting tumor extracellular proteases to target radiosensitizer delivery

Abstract Patients with locally advanced cancers are treated with combined radiotherapy and chemotherapy, however curability is poor and side effects severe. Drugs that sensitize tumors to radiotherapy have been tried to improve cure, but tumor specificity remains a challenge. To achieve tumor selectivity of small molecule radiosensitizers, we tested as a strategy active tumor targeting utilizing peptide-based drug conjugates that split the responsibilities for targeting and radiosensitization into distinct molecular tasks. The tumor milieu possesses localizing beacons that can guide drug delivery using tumor cell surface receptors and microenvironment extracellular matrix metalloproteinases (MMPs). Here we applied peptide-based linkers to test for tumor selective drug delivery and radiosensitization by chemically conjugating the DNA damage checkpoint kinase 1/2 inhibitor AZD7762 to antibody to or cell penetrating peptides. AZD7762 governs DNA damage response and irradiated cell fate. We synthesized drug conjugates of AZD7762 and compared their anti-tumor efficacy in combination with ionizing radiation (IR). An antibody drug conjugate (ADC) was built by attaching AZD7762 to the anti-EGFR antibody cetuximab. Polycationic cell penetrating peptide drug conjugates were constructed by linking AZD7762 to a 9 amino acid repeat of D-arginine and keeping it bare (r9-AZD7762) or cloaking r9 within a MMP-2/9 triggered activatable cell penetrating peptide scaffold (ACPP-AZD7762). In contrast to receptor directed ADCs, ACPPs redirect extracellular tumor microenvironment proteases to guide drug delivery. Intact, ACPPs are charge neutral which blocks the conjugated drug from cell entry. Upon cleavage by tumor overexpressed MMPs, the ACPP scaffold releases drug conjugated polycationic peptide which is then internalized by cells. We found that while cetuximab-AZD7762 ADC had high affinity for EGFR overexpressing tumor cells and prolonged blood circulation in murine models, cetuximab-AZD7762 lacked anti-tumor efficacy. On the other extreme, naked r9-AZD7762 drug conjugate was indiscriminately cytotoxic and radiosensitized a panel of tumor cell lines in cell culture: CAL27, A549, PANC1 and HCT116. However, r9 cell penetrating peptides lacked tumor specificity when intravenously injected into mice. In contrast, MMP-2/9 sensitive ACPPs balanced tumor selectivity with drug efficacy. Intact, ACPPs held conjugated AZD7762 in a pro-drug inactive state that upon tumor microenvironment ACPP cleavage resulted in tumor selective drug accumulation and anti-tumor efficacy in combination with IR. Importantly, a control non-cleavable ACPP-AZD7762 did not improve tumor control with IR, demonstrating the necessity of ACPP cleavage to release active drug. These results highlight the utility of the ACPP technology platform to target amine containing radiosensitizing drugs to tumor tissues based on extracellular protease activity that overcome the limitations of ADC conjugated radiosensitizers. Citation Format: Dina V. Hingorani, Maria F. Camargo, Maryam A. Quraishi, Joseph Aguilera, Stephen R. Adams, Sunil J. Advani. Redirecting tumor extracellular proteases to target radiosensitizer delivery [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6272.

Abstract 2910: A novel Sortilin-targeted docetaxel peptide conjugate (TH1902), for the treatment of Sortilin-positive (SORT1+) triple-negative breast cancer

Abstract Rational: Breast cancers are comprised of several subtypes that share similar clinicopathological features, but that also exhibit several different biological characteristics. Triple-negative breast cancer (TNBC), which comprises 10-20% of breast cancers, or ~ 170,000 new cases per year worldwide and 70% of the basal-like subtype of breast cancers, is a cancer that does not express estrogen receptor (ER), progesterone receptor (PR) or human epidermal growth factor receptor 2 (HER2). TNBC is considered more aggressive than other breast cancers and more difficult to treat because it still lacks a defined molecular signature. Over the last decade, the targeting of specific cancer cell surface receptors has emerged among the best anticancer strategies. Recently, increased expression of the Sortilin receptor (SORT1) has been reported in TNBC patients. Procedures: Given SORT1 functions in protein internalization, sorting and trafficking, we designed a new anticancer peptide-drug conjugation strategy to target SORT1-positive TNBC by linking Docetaxel to a peptide (TH19P01) that specifically binds to SORT1. Results: In vitro, the Docetaxel-TH19P01 conjugate (TH1902) exerted potent anti-proliferative and anti-migratory activities when tested on TNBC-derived MDA-MB-231 cells. The apoptotic and anti-migratory effects induced by TH1902 were reversed by neurotensin and progranulin, two SORT1 ligands, and upon siRNA-mediated silencing of SORT1. Similar to other taxanes, once internalized in the cancer cell, TH1902 altered microtubule polymerization. In vivo, i.v. administration of TH1902 led to greater tumor regression in a murine MDA-MB-231 xenograft tumor and a dose response was observed for TH1902. When docetaxel was injected i.v. at ¼ of its MTD (3.75 mg/kg/week), it had no apparent effect on tumor burden, compared to animals injected with vehicle alone. In contrast, a strong tumor growth inhibition (100%) and sustained effects were observed in mice treated with TH1902 at 8.75 mg/kg/week (equivalent to docetaxel dose of 3.75 mg/kg/week). At higher dose (35 mg/kg/week), a complete tumor regression was seen in mice, and near-total regression (75%) was found with the 17.5 mg/kg/week dosage. While the decreased neutrophil counts subsequent to administration of docetaxel (15 mg/kg/week) were statistically significant after the first intravenous injection, there was no apparent change in the neutrophil counts for mice which received up to 6 cycles of TH1902 (35 mg/kg/week). Conclusion: Taken together, these pre-clinical data demonstrate high in vivo efficacy and safety of TH1902 against TNBC through a SORT1 receptor-mediated mechanism. This novel approach allows for selective targeting of SORT1-positive breast cancers and makes TH1902 a promising clinical candidate for personalized therapy in the treatment of TNBC. Citation Format: Christian Marsolais, Cyndia Charfi, Michel Demeule, Jean-Christophe Currie, Alain Larocque, Alain Zgheib, Natacha Duquette, Richard Béliveau, Borhane Annabi. A novel Sortilin-targeted docetaxel peptide conjugate (TH1902), for the treatment of Sortilin-positive (SORT1+) triple-negative breast cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2910.

Abstract 1843: Melflufen efficacy in multiple myeloma with TP53 aberrations

Abstract Introduction Multiple myeloma (MM) is an incurable plasma cell malignancy characterized by clonal evolution and heterogeneous genetic abnormalities. Deletion of the short arm of chromosome 17 (del17p) harboring TP53 is a high-risk abnormality associated with aggressive disease and therapy resistance. Here, we tested in vitro and ex vivo efficacy of a peptide-drug conjugate melflufen, currently in phase 3 clinical trials for relapsed/refractory multiple myeloma (RRMM), in an isogenic myeloma p53-abrogated cell line model and patient samples. Methods Efficacy of melflufen versus melphalan was tested in the AMO-1 cell line, which displays biallelic wildtype TP53 and retains aspects of a functional p53 system, and AMO-1 clones with either complete loss of p53 or expressing point-mutated p53 protein (R282W hotspot mutation), created using the CRISPR/Cas9 system and modified via Sleeping Beauty vectors. We assessed toxicity and apoptosis using Annexin V and Alamar blue assays. Ex vivo sensitivity to the drugs was examined by flow cytometry in CD138+ plasma cells isolated from MM patients with confirmed del17p or TP53 mutations. We also analyzed response rates in a subpopulation of patients with confirmed del17p from OP-106 HORIZON, an ongoing phase 2 study evaluating the efficacy of melflufen plus dexamethasone in patients with RRMM (NCT02963493). Results Whereas loss of p53 functionality strongly impaired melphalan induced cytotoxicity in the AMO-1 MM cell line model system, treatment with melflufen showed superior efficacy in the parental cells, and was effective independent of the respective TP53 status. Although at low dosages wild-type cells were still more sensitive, in contrast to melphalan this effect was overcome by slight dose increases of melflufen, due to the much steeper dose-effect relationships in the p53 deficient sublines. In contrast to melphalan, the melflufen effect was only partially blocked by combined pre-treatment with inhibitors of apoptosis and necroptosis. Similar results were observed in patient-derived material with melflufen displaying superior activity towards TP53 mutated plasma cells. Analysis of OP-106 HORIZON trial data showed comparable ORR of 20% (CI 95% 4.3-48.1) in the del17p subpopulation (n=15) to 26.2% (CI 95% 18.8-34.6) in the total population (n=136). Conclusions Melflufen is able to trigger myeloma cell death regardless of p53 status, and thus overcome p53-deficiency-mediated melphalan resistance. It demonstrates better ex vivo efficacy in MM patient derived plasma cells harboring del17p or TP53 mutations. Melflufen response rates in the del17p Citation Format: Ana Slipicevic, Umair Munawar, Thorsten Stühmer, Johan Aschan, Fredrik Lehmann, Nina N. Nupponen, Juho Miettinen, Maiju-Emilia Huppunen, Caroline A. Heckman, María-Victoria Mateos, Paula Rodríguez Otero, Paul Richardson, Ralf Bargou. Melflufen efficacy in multiple myeloma with TP53 aberrations [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1843.

Tumour sensitization via the extended intratumoural release of a STING agonist and camptothecin from a self-assembled hydrogel.

Tumours with an immunosuppressive microenvironment respond poorly to therapy. Activation of the stimulator of interferon genes (STING) pathway can enhance intratumoural immune activation, but STING agonists are associated with high toxicity and degrade prematurely, which limits their effectiveness. Here, we show that the extended intratumoural release of the STING agonist cyclic di-AMP transforms the tumour microenvironment from immunosuppressive to immunostimulatory, increasing the efficacy of antitumour therapies. The STING agonist was electrostatically complexed with nanotubes comprising a peptide-drug conjugate (a peptide that binds to the protein neuropilin-1, which is highly expressed in tumours, and the chemotherapeutic agent camptothecin) that self-assemble in situ into a supramolecular hydrogel. In multiple mouse models of murine tumours, a single low dose of the STING agonist led to tumour regression and increased animal survival, and to long-term immunological memory and systemic immune surveillance, which protected the mice against tumour recurrence and the formation of metastases. Locally delivered STING agonists could help to reduce tumour immunosuppression and enhance the efficacy of a wide range of cancer therapies.

Drug-Bearing Peptide-Based Nanospheres for the Inhibition of Metastasis and Growth of Cancer.

Employing a peptide-based nanoscale drug delivery system is an effective strategy to overcome the poor therapeutic outcomes of chemotherapeutic drugs. Here, we developed a self-assembling peptide-drug delivery system comprising a self-assembling anticancer peptide (R-lycosin-I), as revealed in our previous study, and 10-hydroxycamptothecin (HCPT) for cancer therapy. The results showed that peptide-drug conjugates (R-L-HCPT) could assemble into nanospheres of 40-60 nm in water. Compared with free HCPT, R-L-HCPT nanospheres not only inhibited tumor growth but also suppressed pulmonary metastatic nodules on B16-F10 cells in vivo. In summary, these results indicated that the self-assembling R-lycosin-I could provide a promising nanoscale platform for delivering small-molecule drugs. Moreover, our study might provide new opportunities for the development of a new class of functional peptide-drug-conjugated systems based on nanomaterials, which could synergistically enhance anticancer outcomes.

Challenge to develop the novel cancer therapeutics using Peptide-Drug Conjugate (Is PDC able to lead innovation for anticancer therapeutics?)

Challenge to develop the novel cancer therapeutics using Peptide-Drug Conjugate (Is PDC able to lead innovation for anticancer therapeutics?)

Peptide-Drug Conjugates and Their Targets in Advanced Cancer Therapies.

Cancer became recently the leading cause of death in industrialized countries. Even though standard treatments achieve significant effects in growth inhibition and tumor elimination, they cause severe side effects as most of the applied drugs exhibit only minor selectivity for the malignant tissue. Hence, specific addressing of tumor cells without affecting healthy tissue is currently a major desire in cancer therapy. Cell surface receptors, which bind peptides are frequently overexpressed on cancer cells and can therefore be considered as promising targets for selective tumor therapy. In this review, the benefits of peptides as tumor homing agents are presented and an overview of the most commonly addressed peptide receptors is given. A special focus was set on the bombesin receptor family and the neuropeptide Y receptor family. In the second part, the specific requirements of peptide-drug conjugates (PDC) and intelligent linker structures as an essential component of PDC are outlined. Furthermore, different drug cargos are presented including classical and recent toxic agents as well as radionuclides for diagnostic and therapeutic approaches. In the last part, boron neutron capture therapy as advanced targeted cancer therapy is introduced and past and recent developments are reviewed.

Hyaluronic acid-shelled, peptide drug conjugate-cored nanomedicine for the treatment of hepatocellular carcinoma.

Peptide-drug conjugate (PDC) is a promising prodrug in drug delivery systems. To fabricate nanostructures with proper molecular design which can self-assemble to spherical morphologies is very important for PDC chemotherapy. In this study, a novel PDC (PDC-DOX2), in which two doxorubicin (DOX) molecules are conjugated onto a short peptide (KIGLFRWR) with self-assembly function, was designed and synthesized. PDC-DOX2 with self-assembly properties forms a spherical structure under hydrophobic interaction in water. Hyaluronic acid (HA) was then coated on PDC-DOX2 micelles to form a HA-shelled, peptide-doxorubicin conjugate-cored nanomedicine (HA@PDC-DOX2). The amount of HA can regulate the particle size and stabilization of HA@PDC-DOX2. In addition, HA can actively enhance the targeting effects of PDC-DOX2 micelles since it can interact with overexpressed receptors in cancer cells. The core-shell structured HA@PDC-DOX2 nanomedicine showed significantly enhanced potency against hepatocellular carcinoma compared to PDC-DOX2 micelles as well as free DOX. In this work, a novel PDC which can self-assemble to spherical morphologies and a core-shell structure HA@PDC-DOX2 nanomedicine are designed and prepared. It provides a convenient strategy for the size control of PDC assemblies and constructs effective PDC-based drug delivery systems for cancer treatment.

A Peptide-Duocarmycin Conjugate Targeting the Thomsen-Friedenreich Antigen Has Potent and Selective Antitumor Activity.

Solid-phase synthesis allowed the rapid generation of a peptide-drug conjugate. A peptide targeting the Thomsen-Friedenreich antigen (TFα) was conjugated to the alkylating subunit of the potent cytotoxin duocarmycin SA. The compound, containing a cathepsin B cleavable linker, was shown to be active and selective against TFα expressing tumor cell lines.

Tumor-Cell-Surface Adherable Peptide-Drug Conjugate Prodrug Nanoparticles Inhibit Tumor Metastasis and Augment Treatment Efficacy.

Cancer metastasis is the main cause of chemotherapeutic failure. Inhibiting the activity of matrix metalloproteinases (MMPs) is a common strategy for reducing metastasis. However, broad-spectrum MMP-inhibitors (MMPI) may cause undesired side effects. Here, we screened a selective MMP2 inhibitor (CCKIGLFRWR) and linked it with doxorubicin (DOX) to produce an amphiphilic peptide-drug conjugate (PDC). Then novel core-shell nanoparticles were self-assembled from PDC core and modified polylysine (MPL) shell. When the particles were passively targeted to the tumor site, the PDC core was exposed for charge switch of the MPL shell, aggregated for its transformation behavior, and specially adhered to the cell membrane. The disulfide bond between the MMPI peptide and DOX was broken via a low concentration of glutathione-mediated reduction in tumor microenvironment. DOX could effectively enter the tumor cells. Meanwhile, the MMPI peptide could selectively inhibit the activity of the MMP2 and effectively inhibit tumor metastasis.

HORIZON (OP-106): An exploratory analysis of time-to-next treatment (TTNT) in patients (pts) with relapsed/refractory multiple myeloma (RRMM) who received melflufen plus dexamethasone (dex).

e20570 Background: Melflufen is a novel peptide-drug conjugate that rapidly delivers a cytotoxic payload into tumor cells. Melflufen + dex showed efficacy and a manageable safety profile in pts with poor-risk, heavily pretreated RRMM in the phase 2 HORIZON study (Mateos et al. ASH 2019. Abs. 1883). For pts with RRMM, longer TTNT is indicative of disease stabilization and clinical benefit and is associated with lower costs (Chen et al. J Manag Care Spec Pharm. 2017). This report of TTNT after melflufen + dex from HORIZON is, to our knowledge, the first report from a trial population with such advanced RRMM. Methods: Pts with RRMM who had received ≥2 prior lines of therapy, including an IMiD and a proteasome inhibitor (PI), and were refractory to pomalidomide and/or an anti-CD38 monoclonal antibody (mAb), received melflufen 40 mg (IV on d1 of each 28-d cycle) + dex 40 mg/wk until disease progression or unacceptable toxicity. The primary endpoint was overall response rate. Secondary endpoints included progression-free survival (PFS) and safety. TTNT was defined as the time from start of melflufen + dex to first subsequent therapy. Results: Overall, 154 pts were treated (data cutoff, Oct 1, 2019); median age was 64.5 y (range, 35-86), 32% had International Staging System stage 3 disease, 38% had high-risk cytogenetics, 32% had extramedullary disease (EMD), the median number of prior therapies was 5 (range, 2-12), and 71% had triple-class refractory MM (IMiD + PI + anti-CD38 mAb). Treatment discontinuation occurred in 108 pts (70%), most commonly due to disease progression (47%) and adverse events (14%). Among 125 pts evaluable for response, with a median follow up of 15.3 mo, the median TTNT was 8.0 mo (95% CI, 7.2-8.9) and the median PFS was 4.2 mo (95% CI, 3.7-4.9). TTNT and PFS were similar in subgroups of pts with triple-class refractory MM and EMD (Table). Subsequent therapies after melflufen + dex will be presented. Conclusions: TTNT in HORIZON (median 5 prior lines) was consistent with previous reports of TTNT in pts with RRMM who received melflufen + dex or other therapies (median 2-4 prior lines) (Bringhen et al. J Clin Oncol. 2019. Abs. 8043). Melflufen + dex is being further evaluated in the phase 3 OCEAN study (NCT03151811) in pts with RRMM who are refractory to lenalidomide. Clinical trial information: NCT02963493. [Table: see text]

Use of a Noninvasive Brain-Penetrating Peptide-Drug Conjugate Strategy to Improve the Delivery of Opioid Pain Relief Medications to the Brain.

The analgesic potency of morphine-6-glucuronide (M6G) has been shown to be 50-fold higher than morphine after intracerebral injection. However, the brain penetration of M6G is significantly lower than morphine, thus limiting its usefulness in pain management. Here, we created new entities by the conjugation of the angiopep-2 peptide (An2) that crosses the blood-brain barrier (BBB) by low-density lipoprotein receptor-related protein 1 receptor-mediated transcytosis with either morphine or M6G. We demonstrated improvement of BBB permeability of these new entities compared with that of unconjugated M6G and morphine. Intravenous or subcutaneous administration of the An2-M6G conjugate exerted greater and more sustained analgesic activity than equivalent doses of either morphine or M6G. Likewise, subcutaneous An2-morphine induced a delayed but prolonged antinociceptive effect. The effects of these conjugates on the gastrointestinal tract motility were also evaluated. An2-morphine significantly reduced the intestinal transit time, whereas An2-M6G exhibited a reduced constipation profile, as compared with an equimolar dose of morphine. In summary, we have developed new brain-penetrant opioid conjugates exhibiting improved analgesia to side effect ratios. These results thus support the use of An2-carrier peptides as an innovative BBB-targeting technology to deliver effective drugs, such as M6G, for pain management. SIGNIFICANCE STATEMENT: The metabolite morphine-6-glucuronide (M6G) does not efficiently cross the blood-brain barrier. The low-density lipoprotein receptor-related protein 1 peptide ligand angiopep-2 may serve as an effective drug delivery system to the brain. Here, we demonstrated that the coupling of M6G to angiopep-2 peptide (An2) improves its brain penetration and significantly increases its analgesic potency. The An2-M6G conjugate has a favorable side effect profile that includes reduction of developing constipation. An2-M6G exhibits a unique pharmacodynamic profile with a better therapeutic window than morphine.

Recent Advances in Peptide-Based Approaches for Cancer Treatment.

Peptide-based pharmaceuticals have recently experienced a renaissance due to their ability to fill the gap between the two main classes of available drugs, small molecules and biologics. Peptides combine the high potency and selectivity typical of large proteins with some of the characteristic advantages of small molecules such as synthetic accessibility, stability and the potential of oral bioavailability. In the present manuscript we review the recent literature on selected peptide-based approaches for cancer treatment, emphasizing recent advances, advantages and challenges of each strategy. One of the applications in which peptide-based approaches have grown rapidly is cancer therapy, with a focus on new and established targets. We describe, with selected examples, some of the novel peptide-based methods for cancer treatment that have been developed in the last few years, ranging from naturally-occurring and modified peptides to peptidedrug conjugates, peptide nanomaterials and peptide-based vaccines. This review brings out the emerging role of peptide-based strategies in oncology research, critically analyzing the advantages and limitations of these approaches and the potential for their development as effective anti-cancer therapies.