When Karl and Philipp Lang were postdocs in Rolf Zinkernagel’s lab, they had no idea that their research on the immune system’s response to lymphocytic choriomeningitis virus (LCMV) would lead to an anticancer therapeutic, let alone a biotech company. Zinkernagel received the Nobel Prize in Physiology or Medicine in 1996 for the work showing that T cell recognition of viral antigens requires a matched major histocompatibility complex (MHC). A quarter of a century later, the brothers are tailoring knowledge of the LCMV immune response for a more prosaic purpose: in 2019, the Langs’ two German institutions, the University of Duisburg-Essen. and the Heinrich Heine University Düsseldorf, spun out Abalos to advance their arenavirus-based cancer virotherapy platform to the clinic with $12 million in a first funding round.
The field of cancer virotherapy has not met unbridled success. To date, just a single oncolytic herpesvirus has reached the US market: Amgen’s Imlygic (talimogene laherparepvec), which was approved for melanoma in 2015 by the US Food and Drug Administration. This followed decades of research and hundreds of clinical trials employing a variety of oncolytic, mostly adenovirus, treatments, many of which have since gone by the wayside.
But as time has progressed, appreciation has grown that a potent immune response, rather than tumor cell lysis, may be key to viral therapeutic efficacy. This is where the Langs’ decades of work looking at just such interactions promise to pay dividends. Christine Engeland, an experimental virologist at Witten/Herdecke University in Heidelberg, Germany says, “Virotherapy is fascinating because it’s the intersection of oncology, tumor biology, virology and immunology. To really understand what you are doing you need expertise in all these areas, especially now that it is seen more as an immunotherapy. It's good to have immunologists looking into this.”
Karl Lang explains this evolution. “Initially, it was thought that you just killed the tumor with the virus, but then it was clear this will not be working as you basically would have to infect all tumor cells, which is probably impossible.” Bringing the immune system to the tumor is what the Langs believe arenaviruses can do. “We know from our work with Zinkernagel that arenaviruses are extremely strong immune activators, ” Karl says. This rationale was enough to get Marcus Kostka to lead the company from Boehringer Venture Fund, which led the intital funding round. “When I started discussions in 2018, I felt that this is an interesting concept, separate from oncolytic viruses because oncolysis as the therapeutic concept we know now is not sufficient.”
The premise underlying Abalos' formation is that viruses (oncolytic or not) have antitumor properties because they can stimulate the immune system through multiple pathways: by introducing new antigens, both viral and non-viral, that are seen as foreign; through pathogen recognition receptors that trigger the innate immune system; and by attracting T cells and cytokines to tumors. The Langs have several publications that demonstrate some of the ways arenaviruses, in particular, accomplish these tasks. In a 2005 Nature Medicine paper, they showed that arenaviruses induce antigen-specific CD8+ T cells in peripheral niches (in the work described, beta islet cells in a study of autoimmunity) only if additional innate signals occur. LCMV, an arenavirus carried by rodents that can cause neural disease in humans, they found, was the strongest inducer of such “inflammatory signals.” In a 2017 Nature Communications paper, they showed that some arenavirus strains propagate preferentially in cancer cells. This site-specific virus propagation, they found, enhances the inflammatory capacity of LCMV and activates several immune components in the tumor, including interferon type 1, inflammatory macrophages, T cells and natural killer cells.
Arenaviruses have other favorable properties contributing to their efficacy. Unlike oncolytic adenoviruses and herpesviruses, which are fairly quickly cleared from the body after infection, arenaviruses induce relatively limited neutralizing antibodies that enable them to persist long enough for a full-blown CD8+ T cell response to unfold in infected organs. Engleland agrees in part: “One thing that is unique [to arenaviruses] is it’s difficult to raise neutralizing antibodies against the LCMV. There is a debate on whether adaptive immunity will abrogate the efficacy of oncolytic viruses,” she says.
In addition, having a RNA genome, arenaviruses can adapt to tumors by mutating and evolving, a property the Langs have exploited by ‘evolving’ viruses in the lab. In preclinical work, they employed 25 different tumor lines, infecting and passaging them up to 150 times. Through this work, they identified 100 different mutations. “We learn from nature, how we can do this in a quicker time,” says Kostka.
In work not yet published, the Langs’ teams have optimized their mutated arenaviruses for increased entry and replication in tumor cells, for reduced tropism to healthy tissue, and for the ability to induce a specific cytokine profile (for example, type 1 interferon response). They screened in several murine tumor models for those mutants that reduce some of the worst side effects observed in these systems. What they were seeking was a multipronged approach, which they feel is necessary due to the complexity of the immune response. And whereas optimized arenaviruses should intrinsically activate multiple immunological pathways, the company is open to combining their viruses with other modalities, such as checkpoint inhibitors, that could have synergistic therapeutic effects. “The virus itself already addresses this to some extent, but optimization and combining it with other modalities, like checkpoint inhibitors, will make it better,” says Kostka.
Arenaviruses have a clinical track record: they were given to people in the seventies, with some promising results and acceptable side effects, which bodes well for their entry into the clinic. Also noteworthy is Vienna-based biotech Hookipa Pharma’s efforts to use arenaviruses as delivery vehicles for tumor-associated antigens in a vaccination approach. Although the two programs employ different strategies, Hookipa’s clinical work supports the notion that arenaviruses can be used safely in the clinic.
Abalos is planning safety studies for early to mid-2023, with clinical studies to follow in 2024, with an additional $37 million coming in a second A round. According to Kostka, once they had achieved their goal of optimizing virus, getting more investors on board was relatively easy. “We were quite quick, by convincing other investors, within 2 months we had investors together,” he says. Choosing indications and combinations is “the million dollar question,” he says. Translating from animal models is limited. “An animal model is only good to address specific questions — like, is this pathway involved? It cannot give you more confidence as to taking this alone,” he says.
The work is still very much a collaboration among the two universities, with six or seven students, and with work being done at the Abalos facility in Dusseldorf. Philipp Lang has nothing but praise for the support that the universities provided. “It was really great. Everybody was excited about the project. They all worked together to make it happen,” he says. As basic scientists, he says they were a bit naive about bringing a therapy to the clinic: “Having this development and seeing it develop in the clinic is like a dream come true.”
Laura DeFrancesco, Pasadena, CA