Question: What genes are drug targets for Fibrodysplasia Ossificans Progressiva (FOP)?

Context:
 Recently, FOP has been associated with a specific mutation of ACVR1, the gene coding for a bone morphogenetic protein type I receptor. 
Small molecule inhibitors of the bone morphogenetic protein (BMP) receptor kinase ALK2 (ACVR1) are needed urgently to treat the progressively debilitating musculoskeletal disease fibrodysplasia ossificans progressiva (FOP).
Dorsomorphin analogues, first identified in zebrafish, remain the only BMP inhibitor chemotype reported to date.
By screening an assay panel of 250 recombinant human kinases we identified a highly selective 2-aminopyridine-based inhibitor K02288 with in vitro activity against ALK2 at low nanomolar concentrations similar to the current lead compound LDN-193189
Here, it is noted that if B cells are found to be the lymphocytes responsible for excess BMP-4 production in FOP, use of Rituximab, a monoclonal anti-CD20 antibody which effectively targets B cells, could be a less permanent and less risky treatment alternative for FOP.
A new mutation of the Noggin gene in a French Fybrodysplasia ossificans progressiva (FOP) family: Fibrodysplasia ossificans progressiva (FOP) is a very rare disease characterized by congenital malformation of the great toes and progressive heterotopic ossification of the muscles.
Localization of the gene for fibrodysplasia ossificans progressiva (FOP) to chromosome 17q21-22.
A new mutation of the noggin gene in a French Fibrodysplasia ossificans progressiva (FOP) family.
Rarely occurring mutation of ACVR1 gene in Moroccan patient with fibrodysplasia ossificans progressiva.
A new mutation of the Noggin gene in a French Fybrodysplasia ossificans progressiva (FOP) family: Fibrodysplasia ossificans progressiva (FOP) is a very rare disease characterized by congenital malformation of the great toes and progressive heterotopic ossification of the muscles
Mutations in the ACVR1 gene are associated with Fibrodysplasia Ossificans Progressiva (FOP), a rare and extremely disabling disorder characterized by congenital malformation of the great toes and progressive heterotopic endochondral ossification in muscles and other non-skeletal tissues
Mutations of the noggin (NOG) and of the activin A type I receptor (ACVR1) genes in a series of twenty-seven French fibrodysplasia ossificans progressiva (FOP) patients
ACVR1, a therapeutic target of fibrodysplasia ossificans progressiva, is negatively regulated by miR-148a.
These mutations represent new targets for therapeutic intervention in this otherwise incurable disease.
In this study, we examined downstream signaling targets to study the BMP-Smad and BMP-p38 mitogen-activated protein kinase (MAPK) pathways in FOP. 
Mutations in the ACVR1 gene are associated with Fibrodysplasia Ossificans Progressiva (FOP), a rare and extremely disabling disorder characterized by congenital malformation of the great toes and progressive heterotopic endochondral ossification in muscles and other non-skeletal tissues. 
Linkage exclusion and mutational analysis of the noggin gene in patients with fibrodysplasia ossificans progressiva (FOP).
Fibrodysplasia ossificans progressiva (FOP), a rare disorder characterized by progressive ossification of connective tissue, is caused by an activating mutation in Acvr1 (the gene that encodes ACVR1/ALK2).
This gene encodes the type I bone morphogenic protein receptor ALK2, with the residues affected identical to those that, when mutated in the germline, give rise to the congenital malformation syndrome fibrodysplasia ossificans progressiva (FOP), resulting in the transformation of soft tissue into bone.
ACVR1, a therapeutic target of fibrodysplasia ossificans progressiva, is negatively regulated by miR-148a.
A new mutation of the noggin gene in a French Fibrodysplasia ossificans progressiva (FOP) family.
Neofunction of ACVR1 in fibrodysplasia ossificans progressiva.
The discovery of the FOP gene establishes a crucial milestone in understanding FOP, reveals a highly conserved target in the BMP signaling pathway for drug development and specifically stimulates therapeutic approaches for the development of inhibitors for ACVR1/ALK2 signaling.
The discovery of the FOP gene establishes a critical milestone in understanding FOP, reveals a highly conserved druggable target in the TGF-beta/bone morphogenetic protein signaling pathway and compels therapeutic approaches for the development of small molecule signal transduction inhibitors for activin-like kinase-2.

Answer:  Recently, FOP has been associated with a specific mutation of ACVR1, the gene coding for a bone morphogenetic protein type I receptor. 
here, it is noted that if b cells are found to be the lymphocytes responsible for excess bmp-4 production in fop, use of rituximab, a monoclonal anti-cd20 antibody which effectively targets b cells, could be a less permanent and less risky treatment alternative for fop.
Inhibitors of ALK2(ACVR1) are used for the treatment of FOP. Current therapies for FOP are Dorsomorphin analogues which function as BMP inhibitor.  if B cells control excess BMP-4 production in FOP, use of Rituximab, a monoclonal which targets B cells, could be a treatment alternative for FOP.
Exact answer: ALK2, BMP