Drug development technology is moving beyond monoclonal antibodies (MABs), which target a single antigen, to treat hematologic malignancies to new MABs and antibody fragments that target two or more distinct antigens.
The first such molecule to be approved by the U.S. Food and Drug Administration (FDA) was blinatumomab in December 2014 for the treatment of patients with Philadelphia chromosome-negative precursor B-cell acute lymphoblastic leukemia (B-ALL), a rare blood cancer. Blinatumomab is a relatively small fusion protein consisting of two single-chain variable fragments arranged in tandem — the first binds to the CD19 surface antigen of all B cells, and the second binds to the CD3 antigen of T cells, bringing T cells into the proximity of B-cell lymphoma cells.
Since then, six next-generation bispecific antibodies, known as T-cell-targeting bispecific antibodies, have been approved by the FDA for a range of hematologic malignancies, including follicular lymphoma (FL) and multiple myeloma (MM).
“This is a growing field, and there is a lot of innovation and also interest in combining these bispecifics with other therapies, including other standard-of-care agents used in lymphoma and myeloma,” said Jack Khouri, MD, a hematologist at Cleveland Clinic in Ohio.
“I am very passionate about the incorporation of immunotherapies for the treatment of blood cancers. It has been exciting to witness the technology development of bispecific antibodies and now trispecific antibodies,” said Elizabeth Lihua Budde, MD, PhD, a hematologist and researcher at City of Hope Duarte Cancer Center in California. “Our goal is to have chemotherapy-free treatments for all hematologic malignancies, and we are very much getting there right now already for FL, in part thanks to bispecific antibodies.”
ASH Clinical News spoke with Dr. Khouri, Dr. Budde, and those developing bi- and trispecific antibodies at pharmaceutical companies about the types of therapies currently available, their utility and limitations, and new technologies and molecules currently in development.
What Are Bispecific Antibodies?
A traditional MAB is composed of four different peptide chains that bind together — two light chains and two heavy chains. A MAB contains two copies of the fragment antigen-binding region (Fab region), made up of a portion of the light and heavy chain, that binds a specific antigen. In a bispecific IgG antibody, a light and heavy chain molecule bind together, and each has a binding site for the same antigen — CD3, for example. Another light and heavy chain pair also bind together and have a binding site to the second antigen — CD20, in the case of mosunetuzumab, for example.
“At Genentech, we began to work out the technology of making bispecific antibodies more efficiently starting in the 1990s,” said Paul Carter, PhD, a former head and current fellow in Genentech’s antibody engineering department, who collaborated in the development of bispecific technologies at Genentech. “There has been much ingenuity of how to make bispecific antibodies efficiently for the clinic. Because of their modular, Lego-like architecture, there are multiple ways to assemble bispecific antibodies, and various good solutions have been developed by academic researchers and drug-developing companies.”
A: Bispecific T-cell engagers bring CD3+ T cells in proximity to
cells expressing tumor antigen. B: Bispecific NK-cell engager.
Image courtesy of the American Society of Hematology
Genentech has used different approaches to efficiently assemble the heterogenous molecules of a bispecific IgG antibody. One approach was the so-called “knobs-into-holes” method,1,2 developed by Dr. Carter and collaborators; a second approach was the in vitro assembly of half-antibodies developed by Christoph Spiess, PhD, Justin Scheer, PhD, and colleagues.3
In the case of mosunetuzumab, a heavy-light chain pairs with a CD3 antigen binding site, and an engineered “hole” is generated in one cell line and purified. The second heavy-light chain pairs with the CD20 antigen binding site, and an engineered “knob” is generated in another cell line and purified. Subsequently, the two antibody halves are brought together such that the knob and hole bind and form heterodimers.
“Back in the 1990s, the manufacturing technology for bispecifics was quite painful. Now we have honed these technologies and moved to the opportunity to find additional creative applications for these molecules and identify additional antigens,” Dr. Carter said.
Targeting Hematologic Malignancies
Currently, bispecific antibodies are available as therapies for several different blood cancers, including different types of lymphomas and MM. The initial laboratory and subsequent clinical proof-of-concept trials for bispecific antibodies have all been conducted for hematologic malignancies, in part because of the knowledge of specific antigens present in hematologic malignancies, such as CD19 and CD20, and B-cell maturation antigen (BCMA).
The therapeutic advantage of a bispecific antibody is its ability to target and sequester the tumor cell together with an effector T cell. “In MM, there is a large problem to overcome, which is the immunosuppressive state of the bone marrow microenvironment,” said Craig Tendler, MD, vice president of clinical development, diagnostics, and global medical affairs for the Oncology Group at Johnson & Johnson. “With bispecific antibodies, our goal has been to turn on the immune system in a specific way, using the CD3 molecule on one arm, while simultaneously directing the immune system to the myeloma cells that express a specific tumor antigen. This allows us to harness the immune system with specificity to eradicate the myeloma cells in the bone marrow microenvironment. Overcoming this immunosuppression is part of an effective therapeutic approach that may ultimately prevent recurrence and resistance.”
CAR T-Cell Therapies Versus Bispecific Antibodies
Along with bispecific antibodies, several chimeric antigen receptor (CAR) T-cell therapies are FDA approved for overlapping indications, including for patients with relapsed or refractory diffuse large B-cell lymphoma (R/R DLBCL). Additionally, some of the CAR T-cell therapies target the same antigen, CD19, as bispecific antibodies. For clinicians, the two immune-based therapies complement each other.
“It’s great that we have these choices for our patients,” Dr. Budde said.
Although CAR T-cell therapy has the advantage of being a one-time treatment, the therapy is bespoke, requiring immune cells from patients that are then engineered and propagated in the lab before being infused into the patient. Additionally, not all patients have immune cells from which CAR T cells can be generated, and some, who have a particularly fast-growing disease, cannot afford to wait the multiple weeks it takes to generate the individualized treatment.
“Some patients are also not eligible for CAR T-cell therapy due to the potential intense side effects, including cytokine release syndrome (CRS),” Dr. Khouri said.
Dr. Budde also emphasized that to increase the number of patients with cancer who receive targeted and immunotherapies instead of chemotherapy, community doctors need to learn about and embrace bispecific antibody use for their patients as a better option to chemotherapy. CAR T-cell therapy is administered in an outpatient setting at some major academic centers, but only in the inpatient setting within community practices. Bispecific antibodies can be delivered to patients in the community setting because dosing levels have been established and side effects are predictable and can be well-managed, according to Dr. Budde.
“At most centers, the initial dose is administered in a hospital setting, but some centers are already moving the entire treatment delivery to an outpatient setting, with trials testing prophylactic IL-6 inhibitors to prevent CRS and other side effects,” Dr. Khouri noted.
The main issue with BCMA-targeted bispecific antibodies for MM, according to Dr. Khouri, is infection risk, but there are mitigation strategies, including intravenous immunoglobulin administration and bispecific dosing modifications. With G protein–coupled receptor, class C, group 5, member D (GPRC5D)-targeting bispecific antibodies, other unprecedented toxicities are seen, such as skin toxicities and dysgeusia, but supportive care measures are being evaluated to mitigate these side effects.
Bispecific Antibody Combination
According to Dr. Khouri, clinical trials are now testing combination therapies that include an FDA-approved bispecific antibody and other immunotherapies or agents with different mechanisms of action in the earlier lines of treatment in both MM and lymphoma.
“The future will be to give bispecific antibodies earlier in the course of a patient’s disease, when their T cells are not yet exhausted and exhibit better fitness and tumor cell–killing capabilities. There is a potential to improve progression-free survival and potentially overall survival by moving these therapies into the frontline and second-line settings,” Dr. Khouri said.
Results of a study presented at the 2023 American Society of Clinical Oncology Annual Meeting showed the combination of talquetamab plus daratumumab had a high response rate of 84.0% after a median 15-month follow-up in the higher-dose cohort of a phase I trial of 90 patients with R/R MM who were heavily pretreated, irrespective of prior treatment with CD38-directed therapy and T-cell redirection therapy.4
The combination of glofitamab plus englumafusp alfa for patients with R/R B-cell non-Hodgkin lymphoma (NHL) is currently in phase I with initial data reported in 2023. Englumafusp alfa is a new bispecific antibody targeting the CD19 antigen and 4-1BB, a costimulatory molecule found on the surface of T cells. The CD3 and 4-1BB molecules have complementary functions with CD3 stimulation resulting in T-cell activation through the so-called “signal 1” pathway, while 4-1BB stimulation activates a costimulatory signal, called “signal 2,” that augments and prolongs T-cell activity. Results presented at the 2023 International Conference on Malignant Lymphoma Annual Meeting showed that the safety profile of the combination was similar to that of glofitamab monotherapy, including the rate of CRS. The best overall response rate was 67.9% among 78 patients with aggressive NHL, and the complete response rate was 47.4%.5
Yet another combination that is being tested is odronextamab plus REGN5837, a costimulatory bispecific that binds to CD22, a B-cell lymphoma antigen, and CD28, a signal 2 molecule found on T cells that stimulates the CD3 pathway to be more effective.6
Beyond Bispecific Antibodies
Given the success of bispecific antibodies, researchers are looking to develop trispecific antibodies, which can bind to three different targets, including on the same cells or on multiple cells.
“From an engineering perspective, the trispecific antibody is a logical next stage in the evolution of bispecific antibodies,” Dr. Carter said. “This is a much newer field that is still evolving, where the manufacturing technology is still being developed. Currently, the approach is to create a trispecific only if there is something that cannot be done with a bispecific or bispecific combination and after we have additional experience with bispecifics and learn about their limitations.”
Currently, Janssen has a trispecific antibody, JNJ-79635322, in a phase I clinical trial for R/R MM.7 The molecule targets both established antigens on MM cells — GPRC5D and BCMA — as well as CD3 on T cells.
In addition, “there are currently over 200 bispecific antibodies in clinical development,” Dr. Carter said. “This is an exciting time in the field with many new ideas being explored, and I expect many more innovative approaches and approvals of these molecules as the drug development community continues to learn how best to use these antibody molecules.”
References
- Atwell S, Ridgway JB, Wells JA, et al. Stable heterodimers from remodeling the domain interface of a homodimer using a phage display library. J Mol Biol. 1997;270(1):26-35.
- Ridgway JB, Presta LG, Carter P. ‘Knobs-into-holes’ engineering of antibody CH3 domains for heavy chain heterodimerization. Protein Eng. 1996;9(7):617-621.
- Spiess C, Merchant M, Huang A, et al. Bispecific antibodies with natural architecture produced by co-culture of bacteria expressing two distinct half-antibodies. Biotechnol. 2013:31(8):753-758.
- Dholaria BR, Weisel K, Manteos MV, et al. Talquetamab (tal) + daratumumab (dara) in patients (pts) with relapsed/refractory multiple myeloma (RRMM): updated TRIMM-2 results. J Clin Oncol. 2023;41(suppl 16):8003.
- Dickinson M, Carlo-Stella C, Morschhauser F, et al. Combining englumafusp alfa with glofitamab is safe and shows promising efficacy in patients suffering from relapsed or refractory B-cell non-Hodgkin lymphoma. Presented at the 2023 International Conference on Malignant Lymphoma Annual Meeting, June 13-17, 2023.
- Regeneron Pharmaceuticals. A trial to study if REGN5837 in combination with odronextamab is safe for participants with aggressive B-cell non-Hodgkin lymphomas (ATHENA-1). Accessed March 13, 2024. https://clinicaltrials.gov/study/NCT05685173.
- Janssen Research & Development, LLC. A study of JNJ-79635322 in participants with relapsed or refractory multiple myeloma or previously treated amyloid light-chain (AL) amyloidosis. Accessed March 13, 2024. https://www.clinicaltrials.gov/study/NCT05652335.
FDA-Approved Bispecific T-cell Engager Antibodies
The FDA approved blinatumomab in 2014 for B-ALL, demonstrating the ability of a single molecule to bring together effector T cells with their target tumor cells. One major limitation of blinatumomab is that, because of the small size of the antibody fragment, its half-life is just under two hours,1 requiring continuous intravenous infusion in patients.
“Blinatumomab was a proof of concept showing that the efficacy of targeting two different antigens is there. The next-generation antibodies are an improvement for patients, allowing various intervals between dosing and allowing subcutaneous versus intravenous administration,” said Elizabeth Lihua Budde, MD, PhD, a hematologist/oncologist and researcher at City of Hope Duarte Cancer Center in California.
Since 2014, the FDA has approved other bispecific antibodies to treat a variety of blood cancers. These bispecific molecules are full-length antibodies with half-lives typical of MABs on the order of up to three weeks. The noncontinuous administration has also helped to improve the toxicity profile.
October 2022: The FDA approved teclistamab, the first bispecific BCMAxCD3 bispecific indicated for adult patients with R/R MM who have received at least four prior lines of therapy, including a proteasome inhibitor, an immunomodulatory agent, and an anti-CD38 monoclonal antibody.2
December 2022: The FDA granted accelerated approval for mosunetuzumab for the treatment of adults with R/R FL after two or more lines of systemic therapy. Mosunetuzumab is a CD20xCD3 T-cell–engaging bispecific antibody that binds to CD20 on B cells and CD3 on T cells. It achieved an 80% overall response rate and a 60% complete response rate among 90 patients in an open-label, multicenter trial that led to its approval.3
May 2023: The CD20xCD3 T-cell–engaging bispecific antibody epcoritamab received FDA accelerated approval for DLBCL not otherwise specified, including DLBCL arising from indolent lymphoma and high-grade B-cell lymphoma after two or more lines of systemic therapy.4
June 2023: Glofitamab, a CD20xCD3 bispecific T-cell engager, received FDA accelerated approval for R/R DLBCL or LBCL arising from FL after two or more lines of systemic therapy.5
August 2023: A second BCMA-directed bispecific antibody, elranatamab-bcmm, received FDA accelerated approval, also targeting CD3 on T cells. Similar to teclistamab, elranatamab is indicated for adults with R/R MM who have received at least four prior lines of therapy, including a proteasome inhibitor, an immunomodulatory agent, and an anti-CD38 MAB.6
August 2023: Talquetamab was granted FDA accelerated approval for adults with R/R MM who have received at least four prior lines of therapy, including a proteasome inhibitor, an immunomodulatory agent, and an anti-CD38 MAB. Talquetamab is a GPRC5D-directed CD3 T-cell engager.7
“The list of available bispecific antibodies to treat blood cancers will become longer and longer,” Dr. Budde said. Currently the FDA is reviewing odronextamab, a CD20xCD3 bispecific antibody for the potential treatment of patients with R/R FL and R/R DLBCL who have progressed after at least two prior systemic therapies.
References
- Portell CA, Wenzell CM, Advani, AS. Clinical and pharmacologic aspects of blinatumomab in the treatment of B-cell acute lymphoblastic leukemia. Clin Pharmacol. 2013;5(Suppl 1):5-11.
- S. Food & Drug Administration. FDA approves teclistamab-cqyv for relapsed or refractory multiple myeloma. October 25, 2022. Accessed March 13, 2024. https://www.fda.gov/drugs/resources-information-approved-drugs/fda-approves-teclistamab-cqyv-relapsed-or-refractory-multiple-myeloma.
- S. Food & Drug Administration. FDA grants accelerated approval to mosunetuzumab-axgb for relapsed or refractory follicular lymphoma. December 23, 2022. Accessed March 13, 2024. https://www.fda.gov/drugs/resources-information-approved-drugs/fda-grants-accelerated-approval-mosunetuzumab-axgb-relapsed-or-refractory-follicular-lymphoma.
- S. Food & Drug Administration. FDA grants accelerated approval to epcoritamab-bysp for relapsed or refractory diffuse large B-cell lymphoma and high-grade B-cell lymphoma. May 19, 2023. Accessed March 13, 2024. https://www.fda.gov/drugs/drug-approvals-and-databases/fda-grants-accelerated-approval-epcoritamab-bysp-relapsed-or-refractory-diffuse-large-b-cell.
- S. Food & Drug Administration. FDA grants accelerated approval to glofitamab-gxbm for selected relapsed or refractory large B-cell lymphomas. June 6, 2023. Accessed March 13, 2024. https://www.fda.gov/drugs/drug-approvals-and-databases/fda-grants-accelerated-approval-glofitamab-gxbm-selected-relapsed-or-refractory-large-b-cell.
- S. Food & Drug Administration. FDA grants accelerated approval to elranatamab-bcmm for multiple myeloma. August 14, 2023. Accessed March 13, 2024. https://www.fda.gov/drugs/resources-information-approved-drugs/fda-grants-accelerated-approval-elranatamab-bcmm-multiple-myeloma.
- S. Food & Drug Administration. FDA D.I.S.C.O. Burst Edition: FDA approvals of Talvey (talquetamab-tgvs) for relapsed or refractory multiple myeloma, and Elrexfio (elranatamab-bcmm) for relapsed or refractory multiple myeloma. September 26, 2023. Accessed March 13, 2024. https://www.fda.gov/drugs/resources-information-approved-drugs/fda-disco-burst-edition-fda-approvals-talvey-talquetamab-tgvs-relapsed-or-refractory-multiple.
