Gene editing (genome engineering) was thought to be science fiction because it started with the deletion or insertion of a DNA sequence at a specific location, increasing its accuracy through a technique called homologous recombination.  This technique was a long and random process, because the desired recombination events occur extremely infrequently (1 in 106-109 cells), presenting enormous challenges to large-scale applications of gene-targeting experiments and as a result, has been limited in most organisms.
            

In the lab, geneticists have been able to cut out HIV, correct sickle-cell anemia and alter cancer cells to make them more susceptible to chemotherapy.  In the future, with this technology, scientists may be able to edit any human gene.

Recently, Feng Zhang of the Broad Institute in Massachusetts, who also worked on the CRISPR/Cas9 system, published his work in collaboration with various other institutions on the CRISPR system using the enzyme Cpf1 instead of Cas9.  It's predicted that this enzyme will help overcome some of the difficulties researchers have encountered as they develop CRISPR-related treatments for human diseases.  Numerous companies have been working with the CRISPR/Cas9 technology to create therapeutic treatments, but none have yet reached clinical trials.  While Cpf1 is still in early research, Zhang believes that "There is little doubt that... there are additional systems with distinctive characteristics that await exploration and could further enhance genome editing and other areas of biotechnology as well as shed light on the evolution of these defense systems."

Here's Zhang perspective on why Cpf1 might be better than Cas9:
          

-Cpf1 uses only one strand of RNA verses Cas9, which uses two strands to guide and reach its target gene.  A single-strand system might be simpler, a cheaper design and an easier delivery system (enzyme-guide complex) into the cells.

-Cpf1 makes staggered double-strand cuts, or "sticky ends," in the target DNA, whereas Cas9 cuts both DNA strands in the same location "blunt ends" once it's delivered into the cell's nucleus.   Zhang et al. wrote that the staggered ends make it easier to insert a new gene after the old one is removed (because these unpaired nucleotides in that gene could only bond in the specific location you wanted it).  This could overcome the hurdles of Cas9 where scientists have said replacing an old gene with a new one using Cas9 has been more difficult than simply cutting out a gene.

-When Cpf1 hones in on a gene, it actually makes the cut off to the side or farther down the DNA strand. Zhang and colleagues wrote that this feature could be "potentially useful" in preserving the target site for subsequent rounds of editing.

-In the Cpf1 protein, Zhang et al identified two enzymes from the Cpf1-family proteins: Acidaminococcus and Lachnospiraceae bacterium with efficient genome-editing activity in human cells. The Cpf1-family proteins are diverse in bacterial species due to the T-rich PAMs of the Cpf1-family allowing for applications in genome editing in organisms, where all characterized mammalian genome-editing proteins require the presence of at least one G, so the T- and T/C-dependent PAMs of Cpf1-family proteins expand the targeting range of RNA-guided genome editing nucleases; one of the primary functions of CRISPR systems.   For Cas9, only a small fraction of bacterial nucleases can function efficiently when heterologously expressed in mammalian cells.

-Francisella cpf1(FnCpf1) and crRNA alone are sufficient for mediating DNA targeting, compared to Cas9 which requires both crRNA and tracrRNA to mediate targeted DNA interference, thus making this feature a way to simplify the design and delivery of genome-editing tools.