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PURPOSEMutations in the HRAS (m HRAS) proto-oncogene occur in 4%-8% of patients with recurrent and/or metastatic (R/M) head and neck squamous cell carcinoma (HNSCC). Tipifarnib is a farnesyltransferase inhibitor that disrupts HRAS function. We evaluated the efficacy of tipifarnib in patients with R/M m HRAS HNSCC.METHODSWe enrolled 30 patients with R/M HNSCC in a single-arm, open-label phase II trial of tipifarnib for m HRAS malignancies; one additional patient was treated on an expanded access program. After an ad hoc analysis of the first 16 patients with HNSCC with m HRAS variant allele frequency (VAF) data, enrollment was limited to those with a m HRAS VAF of ≥ 20% (high VAF). The primary end point was objective response rate. Secondary end points included assessing safety and tolerability. Patients received tipifarnib 600 or 900 mg orally twice daily on days 1-7 and 15-21 of 28-day cycles.RESULTSOf the 22 patients with HNSCC with high VAF, 20 were evaluable for response at the time of data cutoff. Objective response rate for evaluable patients with high-VAF HNSCC was 55% (95% CI, 31.5 to 76.9). Median progression-free survival on tipifarnib was 5.6 months (95% CI, 3.6 to 16.4) versus 3.6 months (95% CI, 1.3 to 5.2) on last prior therapy. Median overall survival was 15.4 months (95% CI, 7.0 to 29.7). The most frequent treatment-emergent adverse events among the 30 patients with HNSCC were anemia (37%) and lymphopenia (13%).CONCLUSIONTipifarnib demonstrated encouraging efficacy in patients with R/M HNSCC with HRAS mutations for whom limited therapeutic options exist ( NCT02383927 ).

e13025 Background: H3B-6545, a highly Selective ERα Covalent Antagonist (SERCA), inactivates both wild-type and mutant ERα by targeting cysteine 530 and enforcing a unique antagonist conformation. At the dose of 450 mg daily, H3B-6545 has a manageable safety profile and demonstrated preliminary single-agent antitumor activity in heavily pretreated ER+, HER2- mBC patients (Hamilton et al, San Antonio Breast Cancer Symposium, 2020). Methods: The study evaluates the safety, pharmacokinetics (PK), and efficacy of H3B-6545 in combination with palbociclib in patients with ER+, HER2- metastatic breast cancer (MBC). The escalation phase enrolls patients with 2 or more prior therapies in the metastatic setting. Up to one prior chemotherapy and up to one prior CDK4/6 inhibitor were allowed. Results: As of January 31, 2021, 10 patients were enrolled; 7 in Cohort 1 (H3B-6545 300 mg QD and palbociclib 100 mg QD) and 3 in Cohort 2 (H3B-6545 300 mg QD and palbociclib 125 mg QD). One patient in Cohort 1 was not evaluable for dose limiting toxicity (DLT) assessment and no DLT was observed in the 6 evaluable patients. One patient discontinued study treatment because of progression and no patients discontinued study treatment due to adverse events (AE). Grade 3 or 4 neutropenia and thrombocytopenia were observed in 4 patients and 1 patient, respectively. One patient had grade 3 hypercalcemia, generalized muscle weakness, hypophosphatemia, fall, and anemia and one patient had grade 3 lipase increase. Four patients had grade 1 bradycardia or sinus bradycardia (asymptomatic) 1 patient had grade 2 sinus bradycardia (symptomatic, no intervention required). Preliminary PK analysis suggested no clinically relevant drug-drug interactions between H3B-6545 and palbociclib, to be confirmed with data from additional cohorts. Recruitment is currently ongoing in Cohort 2. Updated results will be presented. Conclusions: H3B-6545, in combination with palbociclib, was well-tolerated. Clinical trial information: NCT04288089.

e13022 Background: H3B-6545 is a selective, orally available, small molecule antagonist of the estrogen receptor (ER), covalently binding to a cysteine residue at position 530 of both wild-type and the constitutively active mutant ERα proteins. H3B-6545 demonstrated preliminary clinical antitumor activity in breasts cancer patients in phase 1b/2. Methods: This was an open-label phase 1 study to evaluate the relative bioavailability of H3B-6545 from a tablet formulation compared to capsules, and the effect of pantoprazole on the pharmacokinetics of H3B-6545, in healthy post-menopausal women. Subjects were randomized (1:1 ratio) to a combined crossover and fixed sequence 3 periods treatment: A single oral dose (SOD) of 450 mg H3B-6545 fasted on day 1 (capsules or tablets), followed by a 4-day washout; A SOD of 450 mg H3B-6545 fasted on day 5 (crossover formulation from the first period), followed by a 4-day washout; daily oral doses of 40 mg pantoprazole on days 9 to 15 with coadministration of a SOD of 450 mg H3B-6545 (tablets) on day 15. Results: A total of 16 subjects were enrolled and received at least one dose of H3B-6545 and 15 subjects completed all 3 periods. One subject assigned to the tablet/capsule treatment sequence withdrew from the study due to subject decision on day 13 (Period 3), following completion of Period 1 (H3B-6545 tablet) and Period 2 (H3B-6545 capsule). Following a SOD of H3B-6545 capsules alone, tablets alone, or tablets at steady-state QD of pantoprazole, H3B-6545 geometric mean Cmax was about 1070, 1120 and 1330 ng/mL, respectively, AUC was about 16600, 17500 and 18300 ng.h/mL, respectively, half-life was about 11.0, 11.0 and 10.2 hours, respectively, and the median Tmax was about 3.0, 4.0, and 2.0 hours post dose, respectively. The ratio (capsule/tablet) of Cmax and AUC was both about 0.95; steady-state pantoprazole QD increased H3B-6545 Cmax by 20% with no change in AUC. Nine subjects (56.3%) reported at least 1 TEAE during the study with constipation being the most common (43.8%); all TEAEs were mild in severity. There were no SAEs reported. Conclusions: Plasma PK of H3B-6545 is similar between tablets and capsules, and in the absence or presence of pantoprazole. Concurrent use of gastric acid reducers had a minimal effect on H3B-6545 exposure and was not considered clinically meaningful.

6504 Background: HRAS is a proto-oncogene overexpressed and mutated in some human carcinomas. Tipifarnib is a potent and highly selective inhibitor of farnesyltransferase, a critical enzyme for proper HRAS function. Methods: We report data from two phase 2 clinical trials investigating the activity of tipifarnib in HRAS mutant (HRASm) solid tumors: KO-TIP-001 (NCT02383927: Squamous carcinomas [SCC], thyroid and salivary gland tumors, among others) and IST-01 (NCT02535650: Urothelial carcinomas, UC).Primary endpoints were overall response rate (ORR, KO-TIP-001) and progression free survival (PFS) rate at 6 months (IST-01). All pts had RECIST v1.1. measurable disease at study entry. Pts receive a starting dose of tipifarnib of either 600 or 900 mg administered orally twice daily on days 1-7 and 15-21 of 28-day treatment cycles until progression of disease (PD) or unacceptable toxicity. Results: Proof of concept was achieved in studies KO-TIP-001 and IST-01. Based on preliminary efficacy results (Ho, et. al, ESMO 2018), KO-TIP-001 was amended to continue enrolling only in Head & Neck SCC (HNSCC) pts (Cohort 2) and other SCC pts (Cohort 3) with tumors carrying high HRASm variant allele frequency (VAF) >20%. As of 17 October 2019, 21 HNSCC pts meeting the high HRASm VAF criteria had been treated with tipifarnib of whom 18 were efficacy evaluable at data cut off. Pts had received a median of 2 prior systemic regimens. Ten objective responses were observed in 18 evaluable pts for an ORR of 56%. No responses were observed on last therapy prior to study entry. PFS on tipifarnib and on prior last therapy were, respectively, 6.1 and 2.8 months. In addition, 13 pts with recurrent/metastatic salivary gland tumors (SGT) were treated in KO-TIP-001 or in extended access programs. One objective response was observed in 12 (8%) evaluable pts and an additional 7 (58%) had stable disease as best response. Median PFS in SGT pts was 7 months. In IST-01, 224 UC pts were screened of whom 16 (7%) carried HRAS mutations and 15 of those were enrolled into the study. Five responses were observed in 12 evaluable UC pts (42%) and 3 additional pts had tumor size reduction. Median PFS was 5.1 months. Conclusions: Encouraging activity of tipifarnib was observed in HRASm solid tumors. Clinical trial information: NCT02383927, NCT02535650 .

Background: This Phase 2 study (NCT02383927) is a multi-institutional, open-label trial to determine the efficacy and safety of tipifarnib in patients (pts) with locally advanced/unresectable and/or metastatic solid tumors that carry HRAS missense mutations. HRAS is a proto-oncogene that is overexpressed and mutated in head and neck squamous cell carcinomas (HNSCC) and other SCCs. Tipifarnib is a potent and highly selective inhibitor of farnesyltransferase, a critical enzyme for HRAS activity. Methods: Pts received tipifarnib at a starting dose of 600 – 900 mg orally twice daily on days 1-7 and 15-21 of 28-day cycles. Disease assessments were conducted according to RECIST v1.1 criteria. Null hypothesis and objective response of interest were respectively 10% and 30%. Prior to its completion, this study met its primary objective and, based on preliminary efficacy results (Ho, et. al, ESMO 2018), was amended to continue enrolling only pts with HNSCC (Cohort 2) and other SCC tumors (Cohort 3) carrying HRAS missense mutations at a high variant allele frequency (VAF >35% or ≥20% if baseline serum albumin is >3.5 g/dL). Results: As of May 1, 2019, 23 pts with HNSCC and 10 pts with tumors with other SCC histologies have been treated with tipifarnib. Pts had relapsed/refractory disease with a median of 2 prior regimens. Of note, no objective partial responses were observed on their last therapy prior to study entry, including platinum, immunotherapy and cetuximab +/- chemotherapy. In 15 HNSCC pts meeting the HRAS mutation high VAF inclusion criteria, a 53% overall response rate (ORR) was observed, with 8 confirmed partial responses (PR) and 5 disease stabilizations (SD). Two pts await first on-study tumor response assessment. Overall median progression free survival (PFS) was 5.4 mos (95% CI 4.5 to 19.5 mos, N=15); 19 mos (95% CI 5.3 to 19.5 mos) for pts experiencing a PR and 4.5 mos (95% CI 1.6 to 5.4 mos) for those experiencing SD. Median PFS on last prior therapy was 3.2 mos. All pts had at least 1 treatment-emergent adverse event (TEAE). The most frequently observed drug-related Grade >3 TEAEs occurring in ≥10% pts were blood and lymphatic system disorders, gastrointestinal disorders and renal disorders. Conclusions: Encouraging activity of tipifarnib was observed in HRAS mutant HNSCC. Based on these data, a pivotal study (AIM-HN and SEQ-HN Study, NCT03719690) evaluating the efficacy of this agent in HRAS mutant HNSCC (AIM-HN) and the impact of HRAS mutations on first line therapy of HNSCC (SEQ-HN) has been initiated. Citation Format: Alan Ho, Irene Brana, Robert Haddad, Jessica Bauman, Keith Bible, Laurence Faugeras, Sjoukje Oosting, Deborah J Wong, Myung-Ju Ahn, Valentina Boni, Caroline Even, Jerome Fayette, Maria Jose Flor, Kevin Harrington, Sung-Bae Kim, Lisa Licitra, Ioanna Nixon, Nabil F Saba, Cyrus Sayehli, Pol Specenier, Francis Worden, Binaifer Balsara, Jeanne Britt, Vishnu Mishra, Catherine Scholz, Antonio Gualberto. Preliminary results from a phase 2 trial of tipifarnib in squamous cell carcinomas (SCCs) with HRAS mutations [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr PR08. doi:10.1158/1535-7163.TARG-19-PR08

Background: CXCL12 is a negative prognostic factor for head & neck (HNSCC) and pancreatic (PDCA) cancers, among others. Its receptor, CXCR4, is a negative prognostic factor in lymphoma/leukemia. CXCR4 signals in part through RAS species, and the expression of CXCL12 and CXCR4 appears to be itself regulated by farnesylated proteins. We provide evidence that targeting the CXCL12/CXCR4 pathway with the farnesyltransferase inhibitor tipifarnib translates to long term clinical benefit. Methods: Next generation sequencing and analyses of gene expression were conducted in tumor samples from squamous cell carcinoma, lymphoma, and acute myeloid leukemia (AML) patients treated in tipifarnib trials (studies KO-TIP-001, KO-TIP-002, CTEP20), and complemented with analyses of related tumor gene expression databases in TCGA and GEO. Results: Activating HRAS mutations in HNSCC and KRAS mutations in PDCA were mutually exclusive with CXCL12 expression, consistent with a role for RAS downstream from CXCR4. Contrary to KRAS and NRAS, HRAS is exclusively farnesylated, and treatment with tipifarnib in patients (pts) with advanced HNSCC tumors with a HRAS mutation variant allele frequency (VAF) >20% resulted in 8 partial responses (PR) in 14 pts. Two complete responses (CR), 3 PRs and 4 disease stabilizations (90% clinical benefit) were observed in 10 pts with relapsed/refractory peripheral T cell lymphoma overexpressing CXCL12. Decreases in plasma CXCL12 levels during treatment were observed. Seven CRs were observed in 11 elderly/unfit AML pts overexpressing CXCL12 in bone marrow (NRAS wt or unknown). Ex vivo treatment of bone marrow stromal cell cultures with tipifarnib decreased secretion of CXCL12. Finally, based on the reported relationship between CXCL12 expression and the suppression of pain in PDCA, we conducted a retrospective analysis of a phase 3 study of gemcitabine plus tipifarnib (GT) in advanced PDCA. Notably, absence of abdominal pain at study entry was associated with higher median survival in the GT arm (no pain, pain): 10.2 vs 5.9 months, HR=0.52, p Conclusions: The mechanism of action of tipifarnib appears to involve targeting the CXCL12/CXCR4 pathway and demonstrates a crucial association with the tumor microenvironment and objective clinical responses. Citation Format: Antonio Gualberto, Catherine Scholz, Vishnu Mishra, Matthew R. Janes, Linda Kessler, Eric Van Cutsem, Alan L. Ho, Thomas Witzig. Mechanism of action of the farnesyltransferase inhibitor, tipifarnib, and its clinical applications [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT191.

275 Background: Tumor CXCL12 expression identifies patients who may benefit from tipifarnib therapy. In pancreatic cancer, CXCL12 is known to decrease abdominal pain by inducing the migration of pain suppressing Schwann cells to tumor lesions. Given the association between CXCL12 and pain suppression, we investigated whether the absence of patient reported abdominal pain could be a surrogate of clinical benefit from tipifarnib in pancreatic cancer patients. Methods: We conducted a retrospective analysis of a randomized placebo-controlled trial comparing gemcitabine plus tipifarnib (GT) versus gemcitabine plus placebo (GP) in pancreatic adenocarcinoma patients. Tipifarnib was given at 200 mg bid orally continuously; gemcitabine at standard dosing. Primary study end point was overall survival. Results: 688 patients were enrolled of whom 155 (22.5%) reported no abdominal pain at study entry, 81 received GT and 74 GP. Baseline characteristics were balanced in the subset of patients with no reported abdominal pain (GT,GP): median age (63,59), female gender (35%,43%), ECOG 0-1 (89%,90%), metastatic disease (64%,70%), 6-month weight loss >10% (48%,39%), 6-month jaundice history (51%,45%), and prior Whipple surgery (16%,13%). Subjects receiving GT who did not report abdominal pain at study entry had higher frequency of locally advanced disease (36% vs 24%) and 6-month jaundice (51% vs 38%), and lower frequency of lung (6% vs 14%) and peritoneum (4% vs 13%) metastases than those reporting pain. No differences in survival were observed in the overall study. Median overall survival for GT was 193 vs 182 days for GP. Notably, absence of abdominal pain at study entry was associated with higher median survival in the GT arm (no pain, pain): 305 vs 176 days, HR=0.52, p

Background CXCL12 is a chemokine that is essential for the maturation of myeloid and lymphoid cells. Tipifarnib is a potent and selective inhibitor of the enzyme farnesyltransferase (FT). Treatment with this agent may translate to durable responses in subsets of patients (pts) with acute myeloid leukemia (AML), chronic myelomonocytic leukemia (CMML) and peripheral T-cell lymphoma (PTCL) but its mechanism of action in these indications is poorly understood. We have previously reported that tipifarnib interferes with the CXCL12 pathway. Here we show that an interplay between the CXCL12 and IGF1 pathways may define those pts who may experience objective responses with tipifarnib monotherapy. Methods Gene expression profile (GEP) data generated using RNA-Seq and the Affymetrix U133A gene-chips of tumor samples from 129 pts enrolled into tipifarnib trials (CTEP-20, KO-TIP-002,KO-TIP-004, INT-17) were analyzed with respect to study outcomes and complemented with analyses of mRNA expression in data sets from the cBioportal for Cancer Genomics. Gene expression was further validated using RT-PCR assays. RNA-Seq and Whole Exome Sequencing were conducted using standard methodologies. Clinical trial information: NCT00027872, NCT02464228. NCT02807272, NCT00354146. Results In order to improve our understanding of the molecular pathology of tumor CXCL12 overexpression, we investigated GEPs from 8,401 cancer pts in 25 studies available at cBioportal (TCGA, Provisional). Notably, we found a highly significant correlation in the expression of the IGF1 and CXCL12 genes in 19 of those studies. Intriguingly, the highest IGF1/CXCL12 correlations were observed in indications, including AML (ρ=0.698, p Conclusions Pre-treatment tumor CXCL12, IGF1 and IGFBP7 expression may enable the identification of pts susceptible to experience objective responses with tipifarnib monotherapy. These data may contribute to the understanding of the mechanism of action of FT inhibitors. Disclosures Gualberto: Kura Oncology: Employment, Equity Ownership. Mishra:Kura Oncology: Employment, Equity Ownership. Janes:Wellspring Biosciences: Employment, Equity Ownership. Kessler:Kura Oncology: Employment, Equity Ownership.

Background T-cell leukemia and lymphoma (TCL) is a very aggressive and heterogeneous group of hematological malignancies with poor prognosis and inadequate response to current therapies. The standard first-line treatments have resulted in unsatisfactory patient outcomes and unfortunately, targeted treatments are still at a preliminary phase. The RAS/MAPK pathway is crucial for TCR signaling of T-cells and it is deregulated in TCL. We aimed to determine the therapeutic value of farnesyl transferase inhibitor (FTIs) tipifarnib in TCL cell lines. Effects on cell viability, apoptosis, cell cycle and gene expression were evaluated. Tipifarnib blocks the localization of some farnesylated proteins, including some RAS family members, to cellular membranes, thereby inhibiting their activation. Tipifarnib is a potent and specific FTI with prominent anti-proliferative effects. Methods We tested tipifarnib in 18 T-cell leukemia and 4 T-cell lymphoma cell lines for in vitro sensitivity and for biomarker discovery, both genomic and immunohistochemical. We selected cell lines with available genomic data from COSMIC, CCLE or generated by our group. The MAPK, NFAT, NFKB and JAK/STAT pathways were tested by immunohistochemistry analysis under basal conditions. The range of drug concentrations to perform IC50 analysis was established between 0-10,000 nM (ten points), using CellTiter-Glo® Luminescent Cell Viability Assay kit (Promega, Madison, WI, USA) following manufacturer´s instructions at 0h, 48h and 96h. All experiments were done in sextuplet and all numerical data were expressed as the average of the values ± the standard error of the mean. IC50 analyses were performed with GraphPad Prism v5. Clinically-relevant drug sensitivity was defined as IC50 Results 59.1% (n=13) of cell lines were sensitive to tipifarnib at concentrations which are readily achievable in the clinic. RAS, RAS-guanine nucleotide exchange factors (GEFs) and RAS-GTPase activating proteins (GAPs) genes were mutated in 45.5%, 50% and 27.3%, of cell lines respectively, but their mutational status was not associated with drug sensitivity. We found TP53 and DNMT3 mutated in 80% and 33.3% in sensitive cell lines respectively, and in 63.6% and 0% in resistant cell lines. The mutational state of NOTCH1 was associated with tipifarnib sensitivity; 66.7% in sensitive cell lines versus 9.1% in resistant cell lines (p=0.005). ERK activation (MAPK pathway) was significantly associated with drug sensitivity (p=0.046). Conversely, RelB (NFκB pathway) was associated with drug resistance (p=0.007). GSEA analysis showed that tipifarnib downregulated cell cycle, protein localization to membranes, metabolism, and ribosome and mitochondrial activity. The effect of tipifarnib on cell cycle progression and apoptosis was validated by flow cytometry assays. Tipifarnib decreased cellular viability, increased apoptosis and blocked cell cycle progression in G1 phase. GSEA of molecular pathways regulated by tipifarnib identified downregulation of MYC targets and mTOR and MAPK pathways. MYC is a target of NOTCH1, mutated in sensitive cases and associated with tipifarnib sensitivity. Conclusions In vitro response to tipifarnib in T-cell lymphoma and leukemia cell lines can be predicted using several biomarkers. The mutational NOTCH1 status, together with p-ERK (MAPK activation) were associated with increased sensitivity while RelB expression was associated with resistance. Disclosures Gualberto: Kura Oncology: Employment, Equity Ownership. Piris:Takeda: Honoraria; Janssen: Honoraria; Gilead: Honoraria; Kura: Honoraria.

Genomic profiling of squamous tumors has revealed important similarities between lung squamous cell carcinoma (LSCC) and head and neck squamous cell carcinoma (HNSCC). For instance, HRAS is the most commonly mutated RAS species in both LSCC and HNSCC, observed in approximately 2% and 5% of cases, respectively (TCGA, Nature 2013). Tipifarnib is a potent and selective inhibitor of farnesyltransferase (FT) that catalyzes the post-translational attachment of farnesyl groups to proteins that require localization to the inner cell membrane. Although all RAS isoforms (KRAS/NRAS/HRAS) are FT substrates, HRAS is exclusively dependent upon farnesylation for membrane localization and signaling activation, making HRAS mutant tumors uniquely susceptible to tipifarnib mediated inhibition of FT. With limited treatment options, LSCC and HNSCC remain a significant unmet medical need. Recent evidence supports the clinical utility of tipifarnib for treatment of patients with HRAS-mutant HNSCC, and we present herein data supporting a potential utility of tipifarnib in the treatment of HRAS-mutant LSCC. We have characterized the antitumor activity of tipifarnib in CDX and PDX models of squamous cell carcinoma with activating HRAS mutations. Tipifarnib displayed robust antitumor activity in the majority of these models, including lung and head and neck tumors. Six of seven HRAS-mutant lung SCC PDX models responded to tipifarnib treatment with the majority either fully growth-inhibited or undergoing partial or complete regression. Importantly, even LSCC PDX tumors resistant to chemotherapy responded to tipifarnib, suggesting tipifarnib has the potential to offer clinical benefit in patients relapsed or refractory to standard therapies. The activity of tipifarnib in LSCC models is quite similar to that seen in HNSCC PDX models, where tipifarnib also induced regressions consistent with those observed in patients enrolled in the ongoing Phase 2 study in HRAS-mutant SCCHN patients (NCT02383927), including patients refractory to chemotherapy, cetuximab and/or immunotherapy. These data demonstrate that HRAS is a targetable mutation in lung SCC as well as in HNSCC and illustrate the potential for tipifarnib in the treatment of additional HRAS-mutant squamous cell carcinomas. Citation Format: Linda Kessler, Catherine Scholz, Antonio Gualberto, Yi Liu, Francis Burrows. Tipifarnib is highly active in HRAS mutant lung squamous carcinoma tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4917.

Purpose. To evaluate the biologic effects of SU6668 in patients with solid tumors using comprehensive measures of pharmacokinetics (PK), functional imaging, and tissue correlative studies. Experimental design. Eligible patients with tumors accessible for core needle biopsy were treated with SU6668 at doses of 200 or 400 mg/m2/day. Functional computed tomography (CT) scan and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) were performed at baseline and repeated 4 weeks and 12 weeks after treatment for analysis of tumor angiogenesis. The PK was analyzed using a high-performance liquid chromatography assay. Tumor specimens obtained via core needle biopsy at baseline and 4 weeks later were analyzed for the biologic effects of SU6668. Results. Six of a total of seven patients received treatment for at least 3 months and underwent comprehensive correlative studies, including PK, imaging, and tissue biopsy. Functional CT showed that five of six patients had decreased blood flow in tumors in response to treatment, and DCE-MRI results indicated significant change of area under the signal intensity vs. time curve (AUC) and/or maximum slope (maximum rate of signal intensity change) in two of four patients evaluated with this technique. PK studies showed that the mean apparent oral clearance (Cloral) measured on day 1 was 6.3 ± 2.7 L/hr/m2, yielding a mean AUC of 16.6 ± 4.3 mg/L·hr. By day 22, the Cloral was 40% more than that observed on day 1. Conclusion. It is feasible to evaluate the biologic effects of antiangiogenic agents using comprehensive surrogate measures.

Background: HRAS is a proto-oncogene that is mutated in head and neck, bladder, thyroid, and salivary gland tumors, among others. While discovered over 40 years ago, no specific therapies have yet been developed targeting mutant HRAS. Tipifarnib is a potent and highly selective inhibitor of farnesyltransferase, a critical enzyme requisite for HRAS activation. Over 5,000 patients (pts) have been treated with tipifarnib; although responses have been documented in several tumor indications, the mechanisms of response are still poorly understood. Tipifarnib has demonstrated robust activity in HRAS mutant patient derived xenograft (PDX) models of head and neck squamous cell carcinoma (HNSCC) and squamous non-small cell lung cancer that are resistant to standard therapies. This Phase 2 study (NCT02383927) was conducted to test the hypothesis that inhibition of mutant HRAS oncogenic activity with tipifarnib could translate to objective responses in HNSCC pts driven by the HRAS oncogene. Methods: The study was originally designed to enroll pts into 2 single-arm study cohorts: Cohort 1 (thyroid cancer) and Cohort 2 (other solid tumors), each one with a 2-stage design (11+7 evaluable pts) to determine overall response rate (ORR) as the primary objective. This design has 80% power to detect a difference between 10% and 30% ORR at one-sided significance level of 0.087. Two objective responses were needed to be observed in the first stage for each cohort to proceed to stage 2. The study is considered positive if at least 4 responses are observed in one of the 2 cohorts (N=18 each, stages 1 and 2 combined). The prespecified activity goal for the first stage of accrual in Cohort 2 was met and based on data observed in the first stage of this Cohort, ongoing enrollment to the second stage of Cohort 2 was limited to HRAS mutant HNSCC. For enrollment, pts must have an HRAS mutant, locally advanced/unresectable and/or metastatic solid tumor malignancy and RECIST v1.1 measurable disease. Tipifarnib is given at 900 mg orally twice daily on days 1-7 and 15-21 of 28-day cycles. Response assessments are conducted every 8 weeks. Results: As of August 30, 2017, 28 pts have been enrolled. Tipifarnib was generally well tolerated with myelosuppression, gastrointestinal disturbances (nausea, vomiting and diarrhea) and fatigue constituting the most common adverse events (≥30% of pts, all grades). Twenty four pts are currently evaluable for efficacy: 10 in Cohort 1 and 14 in Cohort 2. Stage 1 enrollment continues in Cohort 1. The primary objective was met for Cohort 2 prior to completing full enrollment, with 4 confirmed responses observed out of 14 evaluable pts. Notably, of the 6 pts in Cohort 2 with HNSCC currently evaluable for efficacy, 4 (67%) achieved a confirmed partial response. Three of these pts remain on treatment in cycles 3, 5, and 19, and one subject discontinued at Cycle 21. Two (33%) pts had disease stabilization as best response (4 cycles, ongoing and 7 cycles). Importantly, 4 of these pts were refractory to prior therapies, including regimens containing immunotherapy (pembrolizumab, nivolumab) or cetuximab +/- chemotherapy. None of the 6 HNSCC patients experienced an objective partial response on their last prior therapy. Conclusions: These data suggest that HRAS mutant HNSCC pts may be refractory to standard therapies but can derive prolonged clinical benefit from tipifarnib treatment. Based on the encouraging activity of tipifarnib in pts with HNSCC with HRAS mutations, enrollment continues in this cohort. Citation Format: Alan Ho, Nicole Chau, Deborah J. Wong, Maria E. Cabanillas, Jessica Bauman, Marcia S. Brose, Keith Bible, Valentina Boni, Irene Brana, Charles Ferte, Caroline Even, Francis Burrows, Linda Kessler, Vishnu Mishra, Kelly Magnuson, Catherine Scholz, Antonio Gualberto. Preliminary results from a phase 2 proof of concept trial of tipifarnib in tumors with HRAS mutations [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr LB-A10.