Lonafarnib is a
farnesyltransferase inhibitor (FTI) that has been investigated in a human clinical trial as a treatment for
progeria, which is an extremely rare
genetic disorder in which symptoms resembling aspects of
aging are manifested at a very early age. For those with progeria, research has shown that the drug reduces the prevalence of stroke and
transient ischemic attack, and the prevalence and frequency of headaches while taking the medication. A phase II clinical trial was completed in 2012, which showed that a cocktail of drugs that included lonafarnib and two other drugs met clinical efficacy endpoints that improved the height and diminished the rigidity of the bones of progeria patients. Lonafarnib is a synthetic
tricyclic halogenated carboxamide with
antineoplastic properties. As such, it is used primarily for cancer treatment.
Hepatitis D Ongoing studies and clinical trials have found a correlation of lonafarnib treatment with cure of
hepatitis D (HDV). Up to now, the trials have proven an efficacy of lonafarnib on HDV if combined with
ritonavir, as a supportive treatment for
pegylated interferon alpha therapy.
Mechanism of Action in Cancer Lonafarnib inhibits
FTase, preventing the
farnesylation of
Ras proteins, which are mutated in approximately 30% of human cancers (e.g., pancreatic, colorectal, lung). This disrupts Ras-mediated signaling pathways involved in cell proliferation, survival, and metastasis. Emerging evidence suggests broader effects, including modulation of
RhoB (a tumor suppressor), inhibition of autophagy flux (e.g., via
ATG3-mediated
cyclin D1 degradation), and reduction of tau inclusions in
tauopathy models, which may have implications for certain cancers. Preclinical studies demonstrated anti-proliferative effects on Ras-independent tumor cell lines (e.g., lung, pancreas, colon, prostate, bladder, and hematologic cancers). Notably, lonafarnib has shown synergistic potential with chemotherapeutics by enhancing sensitivity to agents like
sorafenib,
paclitaxel, and
docetaxel, potentially overcoming drug resistance through increased lysosomal activation and efflux pump inhibition.
Clinical Trials and Efficacy Lonafarnib entered clinical development for cancer in the early 2000s, with extensive phase 1-3 trials evaluating it as monotherapy or in combinations. Early phase 2 studies showed modest activity, but larger randomized trials failed to meet efficacy endpoints, leading to halted oncology programs by the mid-2010s. Key findings include:
Monotherapy In advanced breast cancer (phase 2, n=76 women post-chemotherapy/endocrine therapy), continuous or intermittent oral dosing (200 mg BID) yielded objective response rates of 10-14%, but no progression to phase 3 due to limited durability. Refractory head and neck cancer (phase 2, n=15): Minimal responses (50% at low doses (e.g., 5-10 μM). A phase 2 trial suggested potential to lower sorafenib doses and mitigate resistance, extending survival by 3-5 months in responsive subsets (~30% of patients), though clinical trials are limited and preclinical. Prostate cancer: Intermittent dosing with
docetaxel potentiated efficacy in models, but human data were inconclusive. Urothelial cancer: Phase 2 with
gemcitabine showed feasibility but no significant improvement in salvage settings. Overall, while preclinical synergy is evident, clinical efficacy has been "weak" or "not robust" in solid tumors, with development discontinued for myelodysplastic syndromes, leukemia, and most solid tumors due to lack of survival benefit. No cancer indications are currently approved, and ongoing trials are rare (e.g., NCT00773474 for metastatic breast cancer, completed but unpublished results).
Side Effects and Safety Profile Lonafarnib is generally well-tolerated at oncology doses (100-200 mg BID orally), but dose-dependent toxicities limit its use. Common adverse events (≥20% incidence) include: Serious risks include nephrotoxicity, retinal toxicity, and embryo-fetal harm (contraindicated in pregnancy). Drug interactions are significant: Strong CYP3A4 inhibitors (e.g., ketoconazole) increase exposure (AUC up 4-5x), while inducers (e.g., rifampin) decrease it. In cancer trials, discontinuations due to toxicity were ~10-15%. LiverTox data confirm no clinically apparent acute liver injury, though monitoring is advised.
Current Status and Future Directions As of 2025, lonafarnib is not approved or routinely used for cancer treatment. Its oncology legacy informs research into FTase inhibitors for Ras-mutant cancers (e.g., KRAS G12C), but successors like tipifarnib have also faltered. Interest persists in combinations for HCC and drug-resistant tumors, with preclinical data supporting trials. Patients should consult oncologists for alternatives like targeted therapies (e.g., sotorasib for KRAS-mutated NSCLC). For progeria or HDV, it remains a standard option. == References ==