Immunology update/webinar for melanoma by Dr. Weber with a look forward...

Check out the link below for a webinar with slides presented by Jeffrey S. Weber, MD, PhD now of the Laura and Isaac Perlmutter Cancer Center at NYU.  Just click the 'view activity' button at the bottom.  I have included some info off the slides as well as my report of Dr. Weber's applicable comments in red below.  (Sorry for the strange lay out...best I could do without retyping everything!)

Immuno-Oncology 2016 update by Dr. Weber

What’s New in Melanoma 2016?

 Combination immunotherapies and targeted therapies

 Overcoming BRAF resistance

 New immune agonistic molecules

 Novel cytokines and fusion molecules

 Chemokine antibodies

 Bispecific T-cell engaging molecules

 Adoptive cell therapy

 Targeted therapy and immunotherapy

 Masked antibodies

Vemurafenib Plus Atezolizumab in BRAF-Mutant Melanoma—Trial Design

Patients with untreated BRAFV600-mutant unresectable or metastatic melanoma (N = 17)  
Cohorts: 1- atezo and vemurafenib together   2- vemurafenib X 56 days followed by atezo
3- vemurafenib X 28 days  followed by Atezo.  Atezolizumab (an anti PD-L1 anti-body) was given IV q 3 wk at 20 or 15 mg/kg and Vemurafenib was BID at 960 mg during run in, then decreased to 720mg bid.
Confirmed overall response rate:  Cohort 1 - 33%, Cohort 2 - 75 %, Cohort 3 - 100%.  Overall 76% response rate.  Median of 12.2 months.  AE's were manageable with no grade 4.  Additive activity with excellent level of response.  You will hear much more about this combo in the future.

 MASTERKEY-265: A Phase Ib/III Study of T-VEC + Pembrolizumab (NCT02263508)

        Phase Ib:Enrollment from December 2014 to March 2015  (n = 21 ) N = 21 patients, Unresectable stage III or IV melanoma, treatment naive, injectable lesions, no clinically active brain mets, no active herpetic skin lesions or prior complications from herpetic infection.  TVEC intralesional 4ml/treatment was given with pembro 200 mg IV q2wk.  Mild side effects.

Complete response - 12.5%, Partial response - 43.8%. ORR - 56.3%.  Additive effects, may even be better.  Phase 3 study is ongoing.   
           

Epacadostat (an IDO inhibitor) + Pembrolizumab:Preliminary Results

                61 patients were enrolled by September 2, 2015  Safety data on 46 patients (19 melanoma, 7 RCC, 7 NSCLC, 5 transitional cell carcinoma, 4 endometrial adenocarcinoma). Most common all-grade treatment-related AEs were rash (22%), fatigue (17%), nausea (11%), and pruritus (11%).    Grade 3/4 treatment-related AEs occurred in 13% of patients (rash, 7%).   One patient discontinued for a treatment-related AE.  IDO inhibitor did not seem to increase side effects.  Melanoma patients only (n - 18) - 56% ORR.  Melanoma treatment naive patients (n - 16) - 63% ORR.  Weber found these results very promising and comparable to the ipi/nivo combo in regard to response rates but with much milder side effects!!!

 

KEYNOTE-029: Pembrolizumab + Low-Dose Ipilimumab for Advanced Melanoma
 Pembrolizumab 2 mg/kg + ipilimumab 1 mg/kg.  72% received all 4 ipilimumab doses.  36% incidence of grade 3-4 treatment-related AEs.  54% incidence of immune-mediated AEs (17% grade 3/4).   Pembrolizumab 2 mg/kg + ipilimumab 1 mg/kg provided an ORR of 56%, comparable to that previously reported for nivo 1 mg/kg + ipilimumab 3 mg/kg.   Efficacy, safety, and biomarkers to be further analyzed in the full expansion cohort of 153 patients.  So far, the side effects appear to be decreased by decreasing the ipi dose...while response rates remain good.

                 

                        CheckMate 064: Study Design:  Cohort A - nivo 3mg/kg q2wk X6, then ipi 3mg/kg 1 3wk X4.  Cohort B - ipi 3mg/kg 1 3wk X4, then nivo 3mg/kg q2wk X6. Both cohorts were followed with nivo, 3mg/kg q2wk until progression, toxicity, or withdrawal of consent. Toxicities were no different between arms.  Significant difference in response rates due to sequence of drugs.  Nivo followed by ipi gave better results. "A real surprise."
I already had a rant on this one:  Sequential nivo then ipi orr of 41%!

Efficacy Summary Week 13				Week 25
NIVOàIPI (n = 68)		IPIàNIVO (n = 770)		NIVOàIPI (n = 68)		IPIàNIVO (n = 70)
Confirmed ORR, %	--		--		41.2		20.0
Complete response, n	0		0		0		0
Partial response, n	24		7		28		14
Conventional ORR, %	35.3		10.0		47.7		22.6
Progression rate, %	38.2 (26.7–50.8)		61.4 (49.0–72.8)		38.2 (26.7–50.8)		60.0 (47.6–71.5)

Intralesional Immunotherapy With Oncolytic Coxsackievirus A21 (CVA21) 
 Final response and safety data of the open-label, multicenter phaseII CALM (CAVATAK in Late-stageMelanoma) study of intratumoral CVA21 in 57 patients with unresectable stage IIIC/IV melanoma.    The study met its primary endpoint.  22 of 57 (38.6%) evaluable patients with PFS at 6 months.    Median PFS of 4.2 mos.   ORR 28.1%; median TTR 2.8 mos.  1-year survival rate 75.4%.  Median OS and median DOR not reached (16.5 mos follow-up).  Most common AEs were grade 1 fatigue, chills, fever, and injection site reactions; no grade 3/4 AEs observed.  Looks like another promising intralesional therapy.  Will soon have phase 3 study.

Radiotherapy in Combination With Anti-PD-1 Antibodies: Safety and Efficacy

    Retroactively evaluated all patients at Melanoma Institute Australia and Westmead Hospital who had received either pembrolizumab or nivolumab for unresectable stage III/IV melanoma who had sequential or concurrent radiotherapy.     In 32 evaluable patients, 9 (28%) PR and 5 (16%) stable disease.     In 25 patients who had progressed on PD-1 at the start of RT, 7 (28%) subsequent PRs and 3 (12%) CRs, while 5 (20%) continued progressing.    Survival Brain metastases: PFS 2.5 mos, OS 6.8 mos.  Which I think is excellent.   No brain metastases: PFS 4.1 mos, OS 16.4 mos.   

No excess RT toxicity observed except cerebral radionecrosis in 1 patient 3 months after SRS; potential delayed neurotoxicity in 1 patient with multiple small asymptomatic BMs; disproportionate cerebral edema in 1 patient with rapidly progressive BMs.  So, yes, you can deliver radiation to the brain, or elsewhere, safely...there is no excess toxicity if radiation is given with either nivo or pembro.

Clinical Activity To Date: BRAF + MEK + PD-L1 ab MEDI 4736

 Response-evaluable population includes all patients dosed ≥16 weeks prior to the cut-off date with measurable disease at baseline and ≥1 f/u scan (or discontinuation due to death or PD prior to 1st scan).  Dabrafenib (BRAFi) and Trametinib (MEKi) and MEDI 4736 (PD-L1 antibody) were given in various regimens.   Median duration of response has not yet been reached for Cohorts A and B.             *Shorter follow up in Cohort C, with 5 additional patients ongoing with best response of unconfirmed PR.

Clinical activity	Cohort A(n = 26)		Cohort B(n = 19)		Cohort C*(n = 15)
	D + T + M	T + M		T /M (sequential)
ORR, n (%)	18 (69)		4 (21)		2a(13)
DCR (CR + PR + SD), n (%)	26 (100)		15 (79)		12 (80)
SD ≥12 weeks, n (%)b	4 (15)		10 (53)		6 (40)
Ongoing responders, n/N (%)	16/18 (89%)		4/4 (100%)		1/2 (50%)
Range of duration of ongoing response, wks	7.7+ –50.6+		7.9+ –24.7+		7.0+

Very interesting study.  I like this a lot.  Large influx of T-cells with the trio, converting a cold tumor to a hot tumor, leading to an augmentation of T-cell function.  The trio with its 69% response rate, at least gave additive efficacy, if not synergistic, without increased side effects.

Innovative Ideas: Targeted Therapies 

                           Immunotherapy with targeted therapies:

 BRAF + MEK + pembro,  atezo, IPI + HDAC inhibitor, Ipi + nivo + HDAC inhibitor

              Overcoming BRAF resistance by combining with:
Hsp90 inhibitors,   HDAC inhibitors,   PI3 kinase/AKT inhibitors,   ERK inhibitors,   ERBb3 inhibitors
  

Innovative Ideas: Immunotherapy

 “Masked antibodies” have a peptide linker that “masks” the antigen-binding region of antibodies unless it is cleaved by proteases within the tumor (This is the same as the ADC's - antibody drug conjugates.  Post here:  Another antibody drug conjugate)

 IL-12 has been linked to a tumor-targeting antibody

 IL-15/IL-15 receptor alpha fusion proteins to augment binding to effector T cells but not T regulatory cells

 TGF-beta receptor antibody has been linked to a PD-L1 antibody

 Neoantigen-specific T cells can be expanded from tumor-infiltrating lymphocytes and adoptively transferred

 Bispecific T-cell engagers link CD3 and tumor-associated antigens

Prime Points:  Melanoma Immunotherapy

IDO plus pembro trial will have mature data at ASCO
Survival f/u from sequential BMS-064 trial of nivo then ipi vs nivo then ipi

Nivo + CD137 antibody phase I-II trial
LAG-3 antibody + nivo phase I-II trial
OX- 40 antibody phase I trial
IL-15/IL-15 receptor complex phase I trial
Coxsackievirus + pembro phase I-II trial
Ipi + high dose IL=2


Synopsis of final thoughts by Dr. Weber:

"I think we will all agree that it is a very bright era for immunotherapy in melanoma and immunotherapy for cancer in general.  Ipi is a very impressive drug that is more like a shotgun, while anti-PD1 is like a sniper rifle.  Ipi has the capacity to expand a lot of different antigen specific cells whether they are tumor specific or not, and therefore, combining anything with ipi will expand the side effects.  If you look at survival, the plateau on the curve, for melanoma over the last decade it's about 10%.  Long term results from the early ipi trials, 2010 - 2011, we got up to 20% and that was progress.  If you look at the plateau with the PD-1 trials, we're probably at about 30%, which could be construed as a cure...something we now tell our patients for the first time...but I am absolutely not satisfied with a 30% rate of plateau .  So, we may be looking at triple drug therapy or quadruple drug therapy...and tailoring the therapy to the individual patient.  In patients with slow growing, low burden disease with a normal LDH, it's ok to start with immunotherapy before targeted therapy, since the targeted therapy appears to work just as well whether it is given before or after the immunotherapy.  I think most of us agree that in a BRAF mutated patient with high disease burden, that's symptomatic, rapidly progressing with a high LDH, we would all go with BRAF plus MEK.   If BRAF mutated with low disease burden...that's a tough one.   Interestingly, you might argue that you could go either way because BRAF plus MEK drugs work best with a low LDH, with a low tumor burden, while ipi plus nivo works very well with a high LDH or not...so you might counter argue that you might go with the BRAF/MEK for a finite period of time and then come in with the immunotherapy."

More to come it seems!!!  Thanks, ratties. - c

Dendritic cell vaccines. Perhaps this approach will allow vaccines to live up to their potential for melanoma....SOON!!!

Effective clinical responses in metastatic melanoma patients after vaccination with primary myeloid dendritic cells.  Screibelt, Westdorp, Wimmers, et al.  Clin Cancer Res. 2015 Dec 28.

Thus far, dendritic cell (DC)-based immunotherapy of cancer was primarily based on in vitro-generated monocyte-derived DCs, which require extensive in vitro manipulation. Here, we report on a clinical study exploiting primary CD1c+ myeloid DCs, naturally circulating in the blood. Fourteen stage IV melanoma patients, without previous systemic treatment for metastatic disease, received autologous CD1c+ myeloid DCs, activated by only brief (16h) ex vivo culture and loaded with tumor associated antigens of tyrosinase and gp100. Our results show that therapeutic vaccination against melanoma with small amounts (3-10x106) of myeloid DCs is feasible and without substantial toxicity. Four out of fourteen patients showed long-term progression-free survival (12-35 months), which directly correlated with the development of multifunctional CD8+ T cell responses in three of these patients. In particular, high CD107a expression, indicative for cytolytic activity, and IFNγ as well as tumor necrosis factor (TNF)α and CCL4 production was observed. Apparently, these T cell responses are essential to induce tumor regression and promote long-term survival by stalling tumor growth. We show that vaccination of metastatic melanoma patients with primary myeloid DCs is feasible and safe and results in induction of effective anti-tumor immune responses that coincide with improved progression-free survival.

A phase I/IIa clincal trial in Stage IV melanoma of an autologous tumor-dendritic cell fusion (dendritoma) vaccine with low dose interleukin-2.  Greene, Schneble, Jackson, et al. Cancer Immunol Immunother. 2016 Feb 19.

Stage IV melanoma has high mortality, largely unaffected by traditional therapies. Immunotherapy including cytokine therapies and checkpoint inhibitors improves outcomes, but has significant toxicities. In this phase I/IIa trial, we investigated safety and efficacy of a dendritoma vaccine, an active, specific immunotherapy, in stage IV melanoma patients.
Autologous tumor lysate and dendritic cells were fused creating dendritoma vaccines for each patient. Phase I patients were vaccinated every 3 months with IL-2 given for 5 days after initial inoculation. Phase IIa patients were vaccinated every 6 weeks with IL-2 given on days 1, 3 and 5 after initial inoculation. Toxicity and clinical outcomes were assessed.
Twenty-five patients were enrolled and inoculated. All dendritoma and IL-2 toxicities were The dendritoma vaccine has minimal toxicity profile with potential clinical benefit. There was OS advantage for NED stage IV patients, those receiving higher number of doses and increased frequency. Based on these results, we initiated a phase IIb trial utilizing improved dendritoma technology in the adjuvant setting for NED stage III/IV melanoma patients.
 

Favorable overall survival in stage III melanoma patients after adjuvant dendritic cell vaccination.  Bol, Aarntzen, Hout, et al.  Oncoimmunology. 2015 Jun 5.

Melanoma patients with regional metastatic disease are at high risk for recurrence and metastatic disease, despite radical lymph node dissection (RLND). We investigated the immunologic response and clinical outcome to adjuvant dendritic cell (DC) vaccination in melanoma patients with regional metastatic disease who underwent RLND with curative intent. In this retrospective study, 78 melanoma patients with regional lymph node metastasis who underwent RLND received autologous DCs loaded with gp100 and tyrosinase and were analyzed for functional tumor-specific T cell responses in skin-test infiltrating lymphocytes. The study shows that adjuvant DC vaccination in melanoma patients with regional lymph node metastasis is safe and induced functional tumor-specific T cell responses in 71% of the patients. The presence of functional tumor-specific T cells was correlated with a better 2-year overall survival (OS) rate. OS was significantly higher after adjuvant DC vaccination compared to 209 matched controls who underwent RLND without adjuvant DC vaccination, 63.6 mo vs. 31.0 mo. Five-year survival rate increased from 38% to 53%. In summary, in melanoma patients with regional metastatic disease, who are at high risk for recurrence and metastatic disease after RLND, adjuvant DC vaccination is well tolerated. It induced functional tumor-specific immune responses in the majority of patients and these were related to clinical outcome. OS was significantly higher compared to matched controls. A randomized clinical trial is needed to prospectively validate the efficacy of DC vaccination in the adjuvant setting.

Thanks, Ratties!!! - c

 

Immune reactions with anti-PD1 can be SERIOUS!!!!

Autoimmune inner ear disease in a melanoma patient treated with pembrolizumab.  Zibelman, Pollak, Olszanski, et al.  J Immunother Cancer. 2016 Feb 16.

Immune related adverse events affecting various organ systems are a recognized potential consequence of immune checkpoint inhibition. However, autoimmune inner ear disease is one complication not previously associated with the use of checkpoint inhibitors, though it has been reported after adoptive cell immunotherapy.  Here we present what we believe is the first case of autoimmune inner ear disease resulting from treatment with an immune checkpoint inhibitor in a patient with metastatic melanoma. An 82 year old male presented with widespread metastatic mucosal melanoma and was initially treated with the CTLA-4 inhibitor ipilimumab but had progression of disease after four doses. He was subsequently treated with the PD-1 inhibitor pembrolizumab and after two doses the patient noted bilateral hearing loss. Otology evaluation was significant for the development of bilateral sensorineural hearing loss and the patient was started on treatment with bilateral intratympanic dexamethasone injections. He experienced significant recovery of his hearing deficit with the intratympanic injections and restaging imaging after 12 weeks of pembrolizumab demonstrated a dramatic reduction in tumor burden.  Autoimmune inner ear disease has been previously associated with the therapeutic transfer of genetically engineered lymphocytes as an on-target effect of donor T-cells recognizing antigens on cells in the inner ear. It is important for physicians to have a high clinical index of suspicion for the appropriate recognition and management of any potential autoimmune toxicity with checkpoint inhibitors given the variability of presentation and unique aspects of toxicity.

Severe Hyponatremia and Immune Nephritis Following an Initial Infusion of Nivolumab.  Vandiver, Singer, Harshberger.  Target Oncol. 2016 Mar 4. 

Anti-programmed cell death-1 (PD-1) antibodies pembrolizumab and nivolumab are becoming increasingly important in the treatment of melanoma and non-small cell lung cancer. These agents are known to induce many immune-related adverse events, but rapid-onset nephritis and immune-related hyponatremia have not been described to date. We describe the case of an adult patient who developed severe hyponatremia and rapid-onset nephritis following the first infusion of nivolumab for metastatic melanoma.

Pembrolizumab-induced necrotic myositis in a patient with metastatic melanoma.  Vallet, Gaillet, Weiss, et al.  Ann Oncol. 2016 Mar 2.

Toxic Epidermal Necrolysis-like Reaction With Severe Satellite Cell Necrosis Associated With Nivolumab in a Patient With Ipilimumab Refractory Metastatic Melanoma.  Nayar, Briscoe, Fernandez Penas.  J Immunother. 2016 Mar 1.

Nivolumab is a fully humanized monoclonal antibody to PD-1, which has shown improved overall and progression-free survival.  Across studies of nivo, grade 3 or 4 rash has been noted in more than 1% of patients.  We present a case report of a pt with metastatic melanoma...who developed toxic epidermal necrolysis.   A 64 year old female presented with widespread maculopapular skin rash with bullae and areas of skin detachment after receiving 2 doses of nivo for ipi refractory metastatic melanoma (BRAF wild type).  She was initially treated with prednisone, which was soon changed to methylprednisone followed by immunoglubulin with minimal response to the rash. After discussion with Dermatology, she was given cyclosporine and high-dose prednisone with gradual but significant improvement in her rash. Her skin biopsy showed interface dermatitis with a lymphocytic infiltrate in the dermoepidermal junction and apoptotic keratinocytes with focal areas of complete necrosis of the epidermis with minimal infiltrate.

Be sure to talk to your doctor if you think any of these are other side effects may be happening to you!!!! - c

Sew Chaotically! - McCall's Fit and Flare Dress 7244

This dress went together very well.  Wanted you to see the absolutely "Roo" rainbow stripe on the soft grey, fairly substantial knit.  It washes and dries well.  The most work was on the lining!!!  I plan to make a couple of others and will probably just cut another back and front as lining....rather than fool with a facing AND a lining!!!  After reading some reviews on patternreview.com I did leave out the back zip, but did not cut the pieces on the fold...as I wanted to keep the curve.  It worked out just fine, with plenty of room for Roo to slip it off and on.

Isn't she a cutie patootie? (I think the dress is, too!)  Then today....there was this:

In honor of Roo and one of her favorite poets....with her mother's favorite sentiment:

What I can do — I will —
Though it be little as a Daffodil —
That I cannot — must be - Unknown to possibility
                                                             ~ Emily Dickinson
love - c

Endobronchial Melanoma "Little is known...." Hear ye, hear ye....MARCH FORTH!!!!!

Endobronchial Metastases from Melanoma:  A survival analysis.  Chaussende, Hermant, Tazi-Mezlek, et al. Clin Respir J. 2016 Jan 20.

Metastatic spread to the tracheobronchial tree from other than bronchopulmonary tumors is a common clinical problem. However, malignant melanomas, a highly metastatic potential tumor, is rarely metastasing in the airways. Therefore little is known about survival of patients with endobronchial metastasis from melanoma. The aim of our study was to assess survival of patients with endobronchial metastasis of melanomas according to clinical and radiological features, to determine any possible factor affecting survival. This retrospective study included 19 patients who underwent a bronchoscopy from 11 different hospitals. Data about patients' demographics, symptoms, radiographic, endoscopic findings and treatment were investigated to evaluate any possible impact on survival. Endobronchial metastases occurred at a median of 48 months (range 0-120) following the diagnosis of the primary tumor. 73.7% of patients had other proven metastases when the endobronchial involvement was diagnosed. Symptoms are not specific as well as radiological features. Median overall survival of the studied population was 6 months (range 1-46). Factors of poor survival were multiple metastatic sites, pleural and soft tissue metastasis. Different treatment modalities applied in our patients showed no effect on survival. Patients with endobronchial metastasis have overall poor survival, affected by multiple organ involvement, the presence of pleural and soft tissue disease, while no impact on survival has been shown by any treatment applied. Oh, yeah.  Melanoma CAN look like that!!!!  Matter of fact...it did for me:  Got melanoma? Get yourself a melanoma specialist!!!  And even then, your melanoma specialist may not know what you are dealing with.  But, peeps!!!!  I'm still here!  Granted my endobronchial melanoma was more my presentation (albeit 7 and 3 years respectively after two cutaneous primaries!) rather than after melanoma had invaded many organs.  I feel pretty sure, given its small size, that my brain met was an off shoot from my lung mess...rather than the other way around....but, that additional met was present at diagnosis.  And YES!!!!!  You have one rattie, dear researcher peeps, for whom treatment has had an impact on survival!!!!  If heaven forbid this happens to you.....get the best care you can.  Don't listen to answers that make no sense.  Consider treatment even IF you have only "6 months to live"!!!!  I'm still here after a lobectomy of my right upper lung followed by 2 1/2 years of anti-PD1 and my 2010 endobronchial met!!! Hang in there ratties!  We are showing the way...bit by bit...day by day!  And on my favorite day of all days....MARCH FORTH!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!  Love, c

BRAF inhibitors + SRS in brain mets = good. And.... BRAFi resistant tumors may be vulnerable to arginine deprivation or resistance avoided with the addition of APR-246!

Impact on overall survival of the combination of BRAF inhibitors and stereotactic radiosurgery in patients with melanoma brain metastases.  Wolf, Zia, Verma, Pavlick, et al.  J Neurooncol. 2016. Feb 6.

“The aim of this study was to evaluate the impact of BRAF inhibitors on survival outcomes in patients receiving stereotactic radiosurgery (SRS) for melanoma brain metastases. We prospectively collected treatment parameters and outcomes for 80 patients with melanoma brain metastases who underwent SRS. Thirty-five patients harbored the BRAF mutation (BRAF-M) and 45 patients did not (BRAF-WT). The median overall survival from first SRS procedure was 6.7, 11.2 months if treated with a BRAF inhibitor and 4.5 months for BRAF-WT. Actuarial survival rates for BRAF-M patients on an inhibitor were 54 % at 6 months and 41 % at 12 months from the time of SRS. In contrast, BRAF-WT had overall survival rates of 28 % at 6 months and 19 % at 12 months. Overall survival was extended for patients on a BRAF inhibitor at or after the first SRS. The median time to intracranial progression was 3.9 months on a BRAF inhibitor and 1.7 months without. The local control rate for all treated tumors was 92.5 %, with no difference based on BRAF status. Patients with higher KPS, fewer treated intracranial metastases, controlled systemic disease, RPA Class 1 and BRAF-M patients had extended overall survival. Overall, patients with BRAF-M treated with both SRS and BRAF inhibitors, at or after SRS, have increased overall survival from the time of SRS. As patients live longer as a result of more effective systemic and local therapies, close surveillance and early management of intracranial disease with SRS will become increasingly important.”

BRAF inhibitor resistance enhances vulnerability to arginine deprivation in melanoma.  Li, Wu, Chen, et al.  Oncotarget.  2016 Jan 11.

“BRAF inhibitor (BRAFi) has been used for treatment of melanomas harboring V600E mutation. Despite a high initial response rate, resistance to BRAFi is inevitable. Here, we demonstrate that BRAFi-resistant (BR) melanomas are susceptible to arginine deprivation due to inability to initiate re-expression of argininosuccinate synthetase (ASS1, a key enzyme for arginine synthesis) as well as ineffective autophagy. Autophagy and ASS1 re-expression are known to protect melanoma cells from cell death upon arginine deprivation. When melanoma cells become BR cells by long-term in vitro incubation with BRAFi, c-Myc-mediated ASS1 re-expression and the levels of autophagy-associated proteins (AMPK-α1 and Atg5) are attenuated. Furthermore, our study uncovers that downregulation of deubiquitinase USP28 which results in more active c-Myc degradation via ubiquitin-proteasome machinery is the primary mechanism for inability to re-express ASS1 upon arginine deprivation in BR cells. Overexpression of USP28 in BR cells enhances c-Myc expression and hence increases ASS1 transcription upon arginine deprivation, and consequently leads to cell survival. On the other hand, overexpression of Atg5 or AMPK-α1 in BR cells can redirect arginine deprivation-induced apoptosis toward autophagy. The xenograft models also confirm that BR tumors possess lower expression of ASS1 and are hypersensitive to arginine deprivation. These biochemical changes in BRAFi resistance which make them vulnerable to arginine deprivation can be exploited for the future treatment of BR melanoma patients.”

p53 Reactivation by PRIMA-1Met (APR-246) sensitizes V600E/KBRAF melanoma to vemurafenib.  Krayem, Journe, Wiedig, et al.  Eur J Cancer.  2016 Jan 17. “Intrinsic and acquired resistance of metastatic melanoma to V600E/KBRAF and/or MEK inhibitors, which is often caused by activation of the PI3K/AKT survival pathway, represents a major clinical challenge. Given that p53 is capable of antagonizing PI3K/AKT activation we hypothesized that pharmacological restoration of p53 activity may increase the sensitivity of BRAF-mutant melanoma to MAPK-targeted therapy and eventually delay and/or prevent acquisition of drug resistance. To test this possibility we exposed a panel of vemurafenib-sensitive and resistant (innate and acquired) V600E/KBRAF melanomas to a V600E/KBRAF inhibitor (vemurafenib) alone or in combination with a direct p53 activator (PRIMA-1Met/APR-246). Strikingly, PRIMA-1Met synergised with vemurafenib to induce apoptosis and suppress proliferation of V600E/KBRAF melanoma cells in vitro and to inhibit tumor growth in vivo. Importantly, this drug combination decreased the viability of both vemurafenib-sensitive and resistant melanoma cells irrespective of the TP53 status. Notably, p53 reactivation was invariably accompanied by PI3K/AKT pathway inhibition, the activity of which was found as a dominant resistance mechanism to BRAF inhibition in our lines. From all various combinatorial modalities tested, targeting the MAPK and PI3K signalling pathways through p53 reactivation or not, the PRIMA-1Met/vemurafenib combination was the most cytotoxic. We conclude that PRIMA-1Met through its ability to directly reactivate p53 regardless of the mechanism causing its deactivation, and thereby dampen PI3K signalling, sensitizes V600E/KBRAF-positive melanoma to BRAF inhibitors.”

For what it's worth! - c