Biotech: Immunotherapy

A new field was born in 1981 when, independently, Martin Evans at Cambridge Univ and Gail Martin at UC San Francisco isolated embryonic stem cells of the mouse. Stem cells are the mothers of all the cells of our body. Once they specialize in a specific job, they cannot be used to make cells of a different kind, but, before they specialize, when they are still "pluripotent", they can develop into all cell types. The stem cells of the embryo are pluripotent. The stem cells of your nose are adult stem cells: they can develop into nose cells, not into liver cells. For more than a decade these studies were limited to other animals, but then scientists started studying the human embryonic stem cells. William Haseltine coined the expression "regenerative medicine" in 1992. It wasn't until 1998, though, that James Thomson at the University of Wisconsin isolated human embryonic stem cells. This step made it possible for scientists to generate all the building blocks of our body in a laboratory. At this point there was enough commercial interest in the possibilities of regenerative medicine that several companies were created all over the world. In retrospect, some of the most influential were: Cellectis (France, 1999), Mesoblast (Australia, 2004), Capricor Therapeutics (Los Angeles, 2005) and Pharmicell (Germany, 2006). In 2004 the state of California launched a California Institute for Regenerative Medicine that has been helping research in the field.

Another decade went by, with a lot of controversy about the ethical aspects of stem-cell research. In 2006 (at a meeting of the International Society for Stem Cell Research in Toronto) Shinya Yamanaka of Kyoto University in Japan reported that he had converted adult cells into pluripotent stem cells by simply triggering four genes (now known as the "Yamanaka factors": Oct4, Sox2, C-myc and Klf4). These genes are normally active only in embryos. His seminal paper was titled "Induction of Pluripotent Stem Cells" and that became the term for the technology of genetically reprogramming cells to become pluripotent: "Induced Pluripotent Stem" cells or iPS cells. We don't need to get embryonic stem cells from humans, we can create them in the laboratory. Cellectis immediately licensed Yamanaka's patents.

Converting differentiated cells into stem cells is like turning back the biological clock: Yamanaka's procedure reprograms the DNA in the cell to an embryonic state.

In 2011 Pharmicell got approval for the first stem-cell drug, called "Hearticellgram-AMI". Today Mesoblast, that uses its own proprietary kind of cells, is probably the best known actor in regenerative medicine.

Madeline Lancaster at Cambridge University is using pluripotent human cells to grow three-dimensional tissues ("cerebral organoids") that she uses to model how the human brain develops (see her paper "Cerebral Organoids Model Human Brain Development And Microcephaly", 2013).

This field had its share of scandals. Two rank among the biggest scientific scandals of the last century. In 2004 a Korean scientist, Hwang Woo Suk, announced that he had cloned human embryonic stem-cells, but an investigation by his university found that he was lying. In 2014 a young Japanese scientist, Haruko Obokata, announced that she had discovered a way to turn adult cells back into stem-cells, the so called "stimulus-triggered acquisition of pluripotency" (STAP) cells. Her employer, Riken, investigated and found that it was not true. So we need to be cautious about the announcements that come from stem-cell startups.

But now there is indeed an alternative to Yamanaka's procedure to make stem cells: somatic-cell nuclear transfer (SCNT). In 2007 Shoukhrat Mitalipov at the Oregon Health & Science University created SCNT cells in monkeys, and in 2013 he created human embryonic stem cells from cloned embryos ("Human embryonic stem cells derived by somatic cell nuclear transfer", 2013).

When we mix gene therapy and stem-cell research, we obtain tools that look promising for the regeneration of tissues and body parts. They use different approaches, but this kind of research is going on in several laboratories around the world: Ying Liu at the University of Texas at Houston; Guangbin Xia at the University of Florida; Joshua Hare at the University of Miami; Malin Parmar at Lund University in Sweden; etc.

A terrible disease called "severe combined immunodeficiency" (SCID) was the first disease to be treated with gene therapy. Children who have SCID (sometimes called "bubble children") are basically without an immune system. In 1990 William French Anderson at the National Institutes of Health (NIH) in Maryland introduced a gene called ADA (Adenosine Deaminase) into the immune cells of a four-year-old girl, Ashanti DeSilva, who was suffering from SCID. It didn't really work well, but that was the first case of gene therapy. The first big success story came in 2009, when an eight-year-old boy, Corey Haas, who was going blind (a form of blindness caused by mutations in the gene RPE65) regained normal vision thanks to gene therapy performed by Jean Bennett at the Children's Hospital of Philadelphia. In 2013 this hospital spun off the company Spark Therapeutics. Research on "bubble children" continued and after more than 20 years Anderson's original intuition started working. In 2013 Bobby Gaspar at the Great Ormond Street Hospital at University College London reported success in treating children suffering from SCID with genetically-engineered stem cells, and in 2014 Donald Kohn at UCLA cured 18 children born with SCID by introducing the ADA gene into their cells. The first gene-therapy treatment approved in Western countries was Alipogene Tiparvovec, marketed since 2012 as Glybera by the Dutch company UniQure. It treats a very rare condition and it costs more than one million dollars, the most expensive medicine in the world. Obviously it was not a commercial success. But soon (2017?) a second gene-therapy treatment should be approved in Europe: a gene-therapy treatment to treat those "bubble children" born with SCID. It was developed at San Raffaele Institute in Italy and will be marketed by GlaxoSmithKline as Strimvelis.

We increasingly think that T-cells are the secret to improving the immune system. The T-cell (that stands for "thymus cell") is the foot soldier in the army of the immune system: it recognizes and fights the attacking enemies (the "antigens"). This was discovered in 1958 by Jacques Miller at the University of London: he showed that animals without a thymus had a weak immune system. Until then the thymus was considered a useless leftover from evolution: it is actually the organ that keeps us alive on a planet infested with all sorts of enemies for our health. In 1983 Philippa Marrack and John Kappler at the University of Colorado discovered the T-cell receptor (the chemical mechanism of antigen recognition), while, at about the same time, Tak Mak at the University of Toronto and Mark Davis at Stanford University discovered the relevant genes for, respectively, humans and mice: those genes determine how well the T-cells do their job.

In 2015 the big success story was Layla Richards, a one-year-old girl who was cured of an "incurable" cancer (acute lymphoblastic leukaemia, the most common form of childhood leukaemia) at Great Ormond Street Hospital . The baby did not have enough of the T-cells that search and destroy the leukaemia cells. Cellectis scientists using TALENS edited T-cells from healthy donors and created T-cells for her. It is relatively easy to inject outside T-cells into the body, but there are two problems: the foreign T-cells donÎéÎ÷t recognize the body as their own and start killing all sorts of cells in the body that they are supposed tosave, and the body does not recognize the T-cells so it starts fighting them with its own antibodies (like it fights a transplanted organ). Cellectis edited out two genes from the donorÎéÎ÷s T-cells in order to disable both processes. The result is a T-cell called UCART that is "universal", i.e. that can work in any body: UCART stands for Universal Chimeric Antigene Receptor T-cells. The ones used for leukaemia are UCART19 and will be sold by Servier and Pfizer. In 2016 a second baby condemned by the same cancer was cured by the same UCART19 at the same hospital.

Children with epidermolysis bullosa are condemned to a horrible and painful death: their skin literally disintegrates. Doctors in Holland killed two of these so-called "butterfly children" in order to stop their suffering. This disease is caused by a defective gene that does not produce the protein (type-7 collagen) that holds skin layers together. In 1997 Paul Khavari at a medical center in Palo Alto had published a paper titled "Cutaneous Gene Therapy" that explained how gene therapy could help. Almost twenty years later in 2016 a team at Stanford University, where Khavari now leads a laboratory, has used gene therapy to inject the correct gene into stem cells of the child and to grow healthy skin that can then be grafted on the child's wounds. The gene therapy will be commercialized by a Ohio startup called Abeona Therapeutics (acquired in 2015 by Texas-based PlasmaTech), which is a 2013 spinoff of the Nationwide Children's Hospital in Ohio. The problem is that our body sheds most of its cells every year, so this gene therapy has to be renewed almost every year. It is not a solution, but an improvement over killing the child!

The most interesting T-cells for gene therapy are probably the "chimeric antigen receptors" or CAR-T. The first generation of CAR-T therapy appeared in 1991 and was designed to fight AIDS. It was mainly developed by Brian Seed's group at Harvard Medical School, but similar studies were also under way by Art Weiss' group at UC San Francisco and by Richard Klausner's group at the National Institutes of Health in Maryland. It takes a long time to go from the conference paper to an actual "medicine". This first generation of CAR-T went into clinical trial in 1997. In 2003 a pediatric oncologist, Dario Campana at St Jude Children's Research Hospital in Tennessee, found a new way to make CAR-T cells. Using that method in 2010 Carl June's group at the University of Pennsylvania developed a new, more powerful generation of CAR-T therapy. Cells are taken from a patient's immune cells, genetically modified in a laboratory using a virus, and then reintroduced in the patient's immune system: the genetic modification turns them into hunters and killers of the source of the cancer. In 2011 June's group published the paper "Chimeric Antigen Receptor-modified T Cells in Chronic Lymphoid Leukemia" that was a morale boost for the whole field. (Unfortunately he forgot to credit Campana for his fundamental contribution, which caused some controversy later on). In 2017 the Food and Drug Administration (FDA) approved the first gene therapy for cancer treatment in the USA: a commercial version of Carl June's Tisagenlecleucel or CTL019, sold by Novartis as Kymriah. Unfortunately the price is $475,000! Almost at the same time Gilead offered $12 billion to acquire Kite Pharma, founded in 2009 in Los Angeles by the Israeli oncologist Arie Belldegrun, a firm that had started the clinical trial of its own CAR-T therapy. Juno, Bluebird and Cellectis are other biotech companies working in CAR-T. One problem of course is that it took 26 years from the first generation of CAR-T therapy to the commercial product. Will it take another 26 years to the third generation? The second problem is that today this is an art: a specialized laboratory has to engineer CAR-T-cells for each patient. This is time consuming and very expensive.

In 2016 Elizabeth Parrish, who has her own startup in Seattle called Bioviva, performed gene therapy on herself and improved her "telomere score", which is higher among young people and low among older people. She managed to recover the equivalent of 20 years of telomere decline. This telomere decline is only one of the many aspects of the overall aging process, but she also performed other gene therapies on herself to reverse other factors. Time will tell if her "younger blood" really helped her live longer, but gene therapy is certainly becoming more real. In 2016 Robert MacLaren of Oxford University led a successful experiment of gene therapy to restore sight in a rare case of eye disease ("choroideremia"): he added a working gene to the cells of the retina in order to compensate for the defective gene that causes the disease. In 2016 Dusan Bogunovic at Mount Sinai in New York showed that people without the gene ISG15 (about 1 in 10 million people) have a stronger immune system that can fight almost all known viruses: maybe removing that gene will solve forever the problem of pandemics and make vaccines a relic of the past.

The immune system is one of the smartest organs of our body. It is made of several cell types that defend the body against viruses and cancer. The problem of cancer is that sometimes these cells are switched off. One way to switch them on again is to use gene-editing techniques to create "improved" immune cells. The first success story in "immune therapy", based on research by James Allison at UC Berkeley (the pioneer who in 1996 identified the protein CTLA-4 as the "brake" that stopped the immune system from fighting cancer) and by Tasuku Honjo at the University of Kyoto (who in 1994 identified the gene PD-1, or Programmed Cell Death 1, as another "brake"), was Ipilimumab for the treatment of skin cancer. Officially introduced in 2011, this substance activates the part of the immune system that can recognize and destroy cancer cells. This was followed in 2014 by Keytruda, developed by Roger Perlmutter at Merck, a drug that targets PD-1, and by the similar Opdivo, made by Ono in Japan (the drug that saved the life of former US president Jimmy Carter). Ono, that owes Tasuku Honjo's patents, sued Merck and in 2017 Merck paid a lot of money to Ono. The bad news is that this treatment is extremely expensive ($150,000). Wendell Lim at UCSF, who is also the founder of startup Cell Design Labs, focuses on "T-cells", immune cells that identify other cells infected by a virus or a cancer (The latest paper is "Precision Tumor Recognition by T-cells with Combinatorial Antigen-sensing Circuits" in Cell magazine, 2016). Several start-ups are specializing in creating "improved" T-cells, notably Cellectis, founded in 1999 in France, whose technology is used by John Lin's team at Pfizer's San Francisco laboratory, and AbVitro (acquired by Juno Therapeutics in 2015). In 2015 the US government approved the immunotherapy drug Opdivo manufactured by Bristol-Myers Squibb, a cancer medicine that helps the immune system fight the spread of cancer cells. It only works with skin cancer, it has adverse side-effects, it is very expensive, and it is not always successful, but it is a first practical step. Verily (Google's biotech unit) is holding frequent seminars on the idea of engineering cells to boost the immune system. In 2016 Facebook's first president, Sean Parker, donated 250 million dollars to study how to engineer the immune system so it can fight cancer, and hired Jeffrey Bluestone of UC San Francisco to lead this effort.

The first success story of immunotherapy to fight cancer was announced in 2016 by Steven Rosenberg at the National Cancer Institute. Rosenberg's experiments started in 1985 when he led the first trial on humans of IL-2. IL-2 makes T-cells grow. These are then used to infiltrate the tumor (basically, they are transplanted into the region attacked by the cancer) with a procedure called "adoptive cell transfer". In 1996 he improved his procedure thanks to new information about the genes that represent tumor antigens. In 2006 Rosenberg had tried his procedure on 684 cancer patients and was reporting some success in slowing down or even shrinking the tumor. In 2016 he announced that a woman who had colon cancer was free of cancer. For the first time we have healed someone of cancer using targeted immunotherapy.

One of the leaders in T-cell therapy is now Kite Pharma, founded in Los Angeles in 2009 by Israeli oncologist Arie Belldegrun.