Linvoseltamab for Treatment of Relapsed/Refractory Multiple Myeloma.

PURPOSE: We present a phase I/II first-in-human trial evaluating the safety and efficacy of 50 mg and 200 mg doses of linvoseltamab, a B-cell maturation antigen × CD3 bispecific antibody in relapsed/refractory multiple myeloma (RRMM). METHODS: Phase II eligible patients had RRMM that either progressed on/after ≥three lines of therapy including a proteasome inhibitor (PI), an immunomodulatory drug (IMiD), and an anti-CD38 antibody or was triple-class (PI/IMiD/anti-CD38) refractory. Phase II treatment was once a week through week 14 and then once every 2 weeks. Phase II 200 mg patients who achieved a ≥very good partial response by week 24 received linvoseltamab once every 4 weeks. The primary end point in phase II was overall response rate (ORR). RESULTS: Among the 117 patients treated with 200 mg, the median age was 70 years, 39% had high-risk cytogenetics, and 28% had penta-refractory disease. At a median follow-up of 14.3 months, the ORR was 71%, with 50% achieving ≥complete response (CR). In 104 patients treated with 50 mg at a median follow-up of 7.4 months, the ORR was 48%, with 21% achieving ≥CR. The median duration of response (DOR) for 200 mg patients (n = 83) was 29.4 months (95% CI, 19.2 to not evaluable). Among 200 mg patients, the most common adverse events included cytokine release syndrome (35.0% Gr1, 10.3% Gr2, 0.9% Gr3), neutropenia (0.9% Gr2, 18.8% Gr3, 23.1% Gr4), and anemia (3.4% Gr1, 4.3% Gr2, 30.8% Gr3). Immune effector cell-associated neurotoxicity syndrome occurred in 7.7% of patients (2.6% each Gr1, Gr2, Gr3). Infections were reported in 74.4% of patients (33.3% Gr3, 2.6% Gr4); infection frequency and severity declined over time. CONCLUSION: Linvoseltamab 200 mg induced deep and durable responses, with a median DOR of 29.4 months, in patients with RRMM with an acceptable safety profile.

Leupaxin is similar to paxillin in focal adhesion targeting and tyrosine phosphorylation but has distinct roles in cell adhesion and spreading.

Focal adhesion (FA) formation is induced by extracellular matrix-stimulated integrin clustering and activation of receptors for diffusible factors. Leupaxin (LPXN) is a member of the paxillin family of FA proteins expressed in many cancer cell lines. We found activation of gastrin-releasing peptide receptor (GRPr) by bombesin (BN) stimulated LPXN translocation from cytoplasm to FAs. Using mutagenesis, we identified LIM3 as the primary FA targeting domain for LPXN and showed BN-induced LPXN tyrosine phosphorylation on residues 22, 62 and 72. A LIM3 point mutant of LPXN failed to target to FAs and had no BN-stimulated tyrosine phosphorylation. Conversely, a non-phosphorylatable mutant (Y22/62/72F) translocated to FAs after BN addition. Stimulation of FA formation using vinblastine also induced LPXN translocation and tyrosine phosphorylation. Therefore, dynamic LPXN tyrosine phosphorylation requires translocation to FAs. LPXN and paxillin had opposite roles in adhesion to collagen I (CNI) in MDA-MB-231 breast cancer cells. LPXN siRNA stimulated whereas paxillin siRNA inhibited cell adhesion. Knockdown of both LPXN and paxillin behaved similarly to paxillin knockdown alone, suggesting LPXN's function in adhesion might depend on paxillin. Additionally, LPXN regulated cell spreading on CNI but not on fibronectin whereas paxillin knockdown suppressed spreading on both substrates. These results demonstrate that although LPXN and paxillin's FA targeting and tyrosine phosphorylation are similar, each protein has distinct functions.

Systemic therapy for metastatic renal cell carcinoma.

Renal cell cancer (RCC) is the most common form of cancer of the kidney and accounts for approximately 44,000 cases per year in the United States. Historically, only immunotherapy showed activity in metastatic RCC. The improved survival and quality of life for patients with metastatic RCC over the last several years are direct results of advances made in understanding the development of RCC. Three targeted therapies-sunitinib, sorafenib, and temsirolimus-have been approved for use in the United States recently. Current research is aimed at developing new drugs and combining available drugs to improve upon the responses and survival seen with approved single agents.

Alterations in receptor expression or agonist concentration change the pathways gastrin-releasing peptide receptor uses to regulate extracellular signal-regulated kinase.

G protein-coupled receptors activate extracellular signal-regulated kinases (ERKs) via different pathways in different cell types. In this study, we demonstrate that gastrin-releasing peptide receptor (GRPr) regulates ERK through multiple pathways in a single cell type depending upon receptor expression and agonist concentration. We examined stably transfected BALB/c 3T3 fibroblasts expressing GRPr constructs at different levels and treated the cells with several concentrations of bombesin (BN, a GRPr agonist) to activate a variable number of GRPr per cell. GRPr induced two waves of ERK activation and one wave of ERK inhibition. One wave of activation required an intact GRPr carboxyl-terminal domain (CTD). It peaked 6 min after addition of high BN concentration ([BN]) in cells with high GRPr expression. Another wave of activation was CTD-independent. It peaked 2 to 4 min after BN addition in cells when [BN] and/or GRPr expression were lower. The early wave of ERK activation was more sensitive than the later one to pretreatment with Bisindolylmaleimide I (GF 109203X) (a protein kinase C inhibitor) or hypertonic sucrose. Because these two waves of activation differ in time course, dose-response curve, requirement for GRPr CTD, and sensitivity to inhibitors, they result from different signaling pathways. A third pathway in these cells inhibited ERK phosphorylation 2 min after addition of high [BN] in cells with high GRPr expression. Furthermore, a GRPr-expressing human duodenal cancer cell line showed differential sensitivity to GF 109203X throughout BN-induced ERK activation, indicating that GRPr may activate ERK via multiple pathways in cells expressing endogenous GRPr.

Agonist- and protein kinase C-induced phosphorylation have similar functional consequences for gastrin-releasing peptide receptor signaling via Gq.

Acute desensitization of many guanine nucleotide-binding protein-coupled receptors (GPCRs) requires receptor phosphorylation and subsequent binding of an arrestin. GPCRs are substrates for phosphorylation by several classes of kinases. Gastrin-releasing peptide receptor (GRPr) is phosphorylated by a kinase other than protein kinase C (PKC) after exposure to agonist and is also a substrate for PKC-dependent phosphorylation after treatment with 12-O-tetradecanoylphorbol 13-acetate (TPA). Using GRPr mutants, we examined receptor domains required for agonist- and TPA-induced phosphorylation of GRPr and consequences of these phosphorylation events on GRPr signaling via Gq. Agonist- and TPA-stimulated GRPr phosphorylation in cells require an intact carboxyl terminal domain (CTD). GRPr is phosphorylated in vitro by GPCR kinase 2 (GRK2) and multiple PKC isoforms. An intact DRY motif is required for agonist-stimulated phosphorylation in cells, and agonist-dependent GRK2 phosphorylation in vitro. Although GRPr CTD mutants do not show enhanced in vitro coupling to Gq relative to intact GRPr, CTD mutants have more potent Gq-dependent signaling in cells. Acute desensitization involves CTD-independent processes because desensitization can precede ligand binding in intact GRPr and CTD mutants. TPA-mediated impairment of GRPr-Gq signaling in cells also requires an intact CTD. Similar to GRK2 phosphorylation, PKC phosphorylation reduces GRPr-Gq coupling by approximately 80% in vitro. Arrestin translocation to plasma membrane requires agonist, an intact DRY motif, and GRPr phosphorylation. Therefore, agonist- and PKC-induced GRPr phosphorylation sites are in nearby regions of the receptor, and phosphorylation at both sites has similar functional consequences for Gq signaling.

Phase I study of weekly gemcitabine as a radiation sensitizer for unresectable pancreatic cancer.

PURPOSE: To determine the maximal tolerated dose and dose-limiting toxicities (DLTs) of weekly gemcitabine with concurrent radiotherapy (RT) in patients with unresectable adenocarcinoma of the pancreas. METHODS AND MATERIALS: Patients who had locally advanced or recurrent unresectable pancreatic cancer were eligible. Gemcitabine was administered as a 30-min infusion once weekly for a total of five cycles during the course of RT. The starting dose of gemcitabine was 350 mg/m(2)/wk. Doses were escalated by increments of 25% in successive cohorts of 3-6 patients. RT was delivered at 180 cGy/d to a total dose of 5400-5580 cGy to the gross tumor volume. RESULTS: Nineteen patients were entered in this study through three dose levels (350-550 mg/m(2)/wk). The maximal tolerated dose was determined to be 440 mg/m(2)/wk. The DLTs were neutropenia, thrombocytopenia, and failure to receive all five cycles of gemcitabine. Other non-DLTs included 16 Grade III toxicities, which consisted of thrombosis, infection, nausea, vomiting, hypotension, constipation, diarrhea, and fatigue. One patient at each gemcitabine dose level experienced Grade IV vomiting, and the patient at the 550 mg/m(2) dose developed Grade IV anorexia. CONCLUSION: The maximal tolerated dose of gemcitabine when administered as a 30-min infusion once weekly during RT for unresectable pancreatic cancer was found to be 440 mg/m(2)/wk. The DLTs were neutropenia, thrombocytopenia, and failure to receive all five cycles of chemotherapy. Concurrent gemcitabine and RT is reasonably well tolerated and deserves additional evaluation against the current standard of care.