Tuesday, August 23, 2016

Targeted therapies and tumor lysis syndrome

Novel targeted therapies are being approved in clinical trials for many hematologic malignancies. Tumor lysis syndrome (TLS) is being noticed as a novel side effect of many of these agents. A recent review in AJH summarizes the various drugs that have led to TLS as a potential side effect of targeted therapies.

TLS was most common in drug trials dealing with patients with acute leukemias, high grade non Hodgkin’s lymphomas, mantle cell lymphomas, CLL and myeloma. Some of the risk might be tumor related rather than the drug but below are the drugs that could be potential TLS promoting.
Incidence of TLS based on clinical trials for novel targeted therapies

Alvocidib (cyclin dependent kinase inhibitor) – 42% in poor risk AML patients, 13% in CLL patients
Venetoclax( ABT-199)( small molecule B cell lymphoma/leukemia 2 inhibitor)- 2.7-8.9% in CLL
Dinaciclib( cyclin dependent kinase inhibitor)- 15% in patients with AML or ALL and another 15% in CLL
Ibrutinib( Bruton kinase inhibitor)- 6.7% in CLL patients
Dasatinib( BCR-ABL tyrosine kinase inhibitors)- 4.2% in patients with ALL
Lenalidomide( immunomodulatory agent)- 3-4% in CLL patients
Obinutuzumab( anti CD20 agent)- 3-4.8% in CLL patients
Oprozomib( proteasome inhibitor)- 2.4% in various hematologic malignancies
Brentuximab vedotin( anti cd30 antibody)- 1.7% in anaplastic large cell lymphoma patients
Carfilzomib( proteasome inhibitor)- 1% in myeloma patients

Not much found in the two listed below
Idelasib( phosphatidylinositol 3-kinase inhibitor)- No TLS in CLL patients
Ofatumumab( anti CD20 agent)-No TLS in CLL patients



Wednesday, August 17, 2016

Topic Discussion: Euglycemic Diabetic Ketoacidosis


The first time the term Euglycemic DKA(eDKA) was mentioned was in 1973- in British Medical Journal in patients who were diabetic but didn't have the full blown hyperglyecmic part.  Compared to classic DKA, eDKA presents with mild to moderate hyperglycemia typically <300mg/dl blood glucose levels.  


Why is this more important now?

In 2013, many SGLT2 inhibitors got approved for DM management( the glucoretics).  The FDA performed a FAERS search of adverse effects with these agents and 73 cases were identified of ketoacidosis linked to SGLT-2 inhibitors.  All patients required hospitalization, and 60% had DMII. Blood glucose levels ranged from 90mg/dl - 1300mg/dl( median 211).  Timing of onset was around 43 days or starting or dose change of the agent.  Majority of the cases also had dehydration, infection or change in insulin doses.   No mortality has been reported with this effect.  All patients respond quickly with intravenous hydration and insulin once recognized. The FDA did acknowledge that some of the cases occurred in DMI, where it's an off label use. More detail here



Is it a class effect? 
Yes. The initial FDA reporting was done with canagliflozin(invokana). A more recent study found an incidence rate of 0.07% with this agent.  In a large study with dapagliflozin( Farxiga), 0.1% of patients got eDKA.  Empagliflozin(Jardiance) also has been found to cause eDKA. 

What are the risk factors for development of eDKA with SGLT2 inhibitors?

Dehydration
Alcohol use
decrease in insulin use
Infection
Low carbohydrate diet
Reduction in caloric intake
Advance age

Mechanism of action

Ketosis results from restriction of carbohydrate usage with increased reliance on fat oxidation for energy production. The pathogenesis of hyperglyemic DKA is well established. Since SGLT2 are glucoretics as described before, they can lead to volume depletion- like a diuretic and perhaps leading to a "starvation" like ketoacidosis with normal glucose levels. SGLT2 induced glycosuria can happen over 24 hours and this artificial low plasma glucose do not stimulate insulin. In eDKA, insulin deficiency and insulin resistance are milder; therefore, glucose overproduction and under-utilization are quantitatively lesser than in DKA. More importantly, renal glucose clearance (i.e., the ratio of glycosuria to prevailing glycemia) is twice as large with eDKA than with DKA. Ketoacidosis follows with the same sequence of events in eDKA as in DKA. Insufficient insulin levels will then decrease glucose utilization and promote lipolysis and ketogenesis. In addition, these drugs can increase glucagon levels leading to increase ketone production.

In summary, eDKA is pathophysiologically similar to DKA except for the circumstance—SGLT2-induced glycosuria—that “artificially” lowers plasma glucose levels and predisposes to increased ketogenesis.

Prevention and treatment

Blood and urine monitoring of ketones is essential especially when patients get ill or are experiencing one of the risk factors.  Adequate hydration and carbohydrate intake will help and holding the offending agent is indicated.  No data exists on a safe time to restart the agent. 

Here is a nice review on this topic
http://onlinelibrary.wiley.com/doi/10.1111/jdi.12401/pdf

Thursday, August 4, 2016

TOPIC DISCUSSION: New anti retrovirals and the kidney

As HIV becomes a chronic illness, novel agents to combat this virus have been out in the last decade. We are familiar with the renal toxicities of tenofivir for many years. Tenofivir is the cisplatin of the ID world.  But what about the new novel agents?
Here is a table that summarizes the new agents and their known or unknown renal toxicities

Drug name( trade)
Mechanism of Action
Renal effect
Excretion
Reference
Rilpivirine(Edurant)
Non nucleoside reverse transcriptase inhibitor
Decreases the secretion of creatinine in the proximal tubule via OCT2 , appear after 1-2 weeks after treatment and can then plateau
Renal


Dolutegravir(Tivicay)
Integrase inhibitor
Decreases the secretion of creatinine in the proximal tubule via OCT2, appear 1-2 weeks after treatment and then plateau
Liver

Cobicistat(Tybost)
Inhibitor liver enzymes so other HIV drugs effect gets enhanced
Decreases in secretion of creatinine  in the apical side of proximal tubule as it inhibits MATE 1 transporter, can be as early as day 7 of start.
Liver


Tenofivir dispoxil fumarate( TDF) is the classic nephrotoxic agent.  It actively taken up by the proximal tubular cell via OAT1 and 3 and released in urinary space by secretion of MDRP-2 and 4. There is a novel tenofivir formulation called tenofivir alafenamide fumrate( TAF) which is used in lower dosage combinations and lower level of parent drug is noted. In addition, TAF does not bind to these organic transporters and hence less renal tubular trafficking. Once out in clinical use, we might see less tenofivir related renal toxicities. 
A lot of combination agents are being used to combat the virus. The list below from FDA approved AIDS website compiles them with their trade names. The most nephrotoxic ones are the ones that contain TDF as expected or one of the above mentioned agents that block creatinine secretion.


abacavir and lamivudine
(abacavir sulfate / lamivudine, ABC / 3TC)
Epzicom
No renal concerns
abacavir, dolutegravir, and lamivudine
(abacavir sulfate / dolutegravir sodium / lamivudine, ABC / DTG / 3TC) 
Triumeq 
Slight increase in creatinine
abacavir, lamivudine, and zidovudine
(abacavir sulfate / lamivudine / zidovudine, ABC / 3TC / ZDV)
Trizivir
No renal concerns
atazanavir and cobicistat
(atazanavir sulfate / cobicistat, ATV / COBI)
Evotaz
Slight increase in creatinine
darunavir and cobicistat
(darunavir ethanolate / cobicistat, DRV / COBI)
Prezcobix
Slight increase in creatinine
efavirenz, emtricitabine, and tenofovir disoproxil fumarate
(efavirenz / emtricitabine / tenofovir, efavirenz / emtricitabine / tenofovir DF, EFV / FTC / TDF)
Atripla
Contains tenofivir- renal toxicity can be present
elvitegravir, cobicistat, emtricitabine, and tenofovir alafenamide fumarate
(elvitegravir / cobicistat / emtricitabine / tenofovir alafenamide, EVG / COBI / FTC / TAF)
Genvoya
Contains tenofivir
Stribild
Contains tenofivir
emtricitabine, rilpivirine, and tenofovir alafenamide
(emtricitabine / rilpivirine / tenofovir AF, emtricitabine / rilpivirine / tenofovir alafenamide fumarate, emtricitabine / rilpivirine hydrochloride / tenofovir AF, emtricitabine / rilpivirine hydrochloride / tenofovir alafenamide, emtricitabine / rilpivirine hydrochloride / tenofovir alafenamide fumarate, FTC / RPV / TAF)
Odefsey
Tenofvir alafenamide does not bind to the proximal tubule transporters and is potentially less nephrotoxic
emtricitabine, rilpivirine, and tenofovir disoproxil fumarate
(emtricitabine / rilpivirine hydrochloride / tenofovir disoproxil fumarate, emtricitabine / rilpivirine / tenofovir, FTC / RPV / TDF)
Complera
Contains tenofivir- hence renal failure can occur and rilpivirine can increase crt as well
emtricitabine and tenofovir alafenamide
(emtricitabine / tenofovir AF, emtricitabine / tenofovir alafenamide fumarate, FTC / TAF)
Descovy 
Novel tenovifir- hence less likely
emtricitabine and tenofovir disoproxil fumarate
(emtricitabine / tenofovir, FTC / TDF)
Truvada
Can cause AKI given tenofivir presence
Combivir
No renal issues
lopinavir and ritonavir
(ritonavir-boosted lopinavir, LPV/r, LPV / RTV)
Kaletra
No renal issues 

Wednesday, July 27, 2016

Consult Rounds: Hyponatremia and Rhabdomyolysis


A lesser known complication of hyponatremia or its correction is rhabdomyolysis. While recognized causes of rhabdomyolysis (Rb) include injury, seizures, drugs such as statins, hypokalemia and hypophosphatemia are known in the literature, less is known re association of hyponatremia leading to Rb.  


It was first described in 1979. In that patient, the low Na was from psychogenic polydipsia.
Multiple case reports following them( listed below) have been described in the literature. Most recently, this has been described in marathon runners that get both hyponatremic and Rb. In that study, the hyponatremic runners with the lowest post race Na demonstrated the highest CPK values at subsequent checkpoints. This is interesting.

What could be the mechanism?  What does the literature say?
1. Change in osmotic pressures results in failure of regulation of cell volume and cell lysis( so this could occur during hyponatremia or treatment of hyponatremia).
If the Na is corrected too rapidly, the cell has no time to compensate for the osmotic shifts and perhaps leads to Rb.
2. Na/Ca pump in muscle cells might be effected. As extracellular Na drops, Ca leaves the muscle cell and ensuing activation of cellular proteases leading to cell lysis.
3. Seizures leading to the rise in CPK

Situations where this has been described in the literature:
Most commonly: Psychogenic polydipsia
Others: use of thiazides, PPIs, Bactrim, marathon runners, adrenal insufficiency

Hmmm... Should we be checking CPKs in our severe hyponatremia cases? Should we be concerned about Rb in rapid correction ( more than CPM) as Rb is likely more commonly seen then CPM?


Here are some interesting references
http://link.springer.com/article/10.1007%2Fs00421-015-3324-4


Monday, July 25, 2016

In the NEWS: Nephrologists compensations on a rise!!


The recently reported AGMA compensation survey suggests that there is an above average increase in the compensation and salaries of Nephrologists nationally in the USA.  The data even suggested an average of 20% increase in salaries compared to hospitalists.


This is important piece of information as currently there is a major drought in applications in nephrology fellowship. While content being difficult, tough physiology and exposure were considerations why residents never applied for nephrology, compensation might have played a major role in choosing alternative specialty of hospital medicine for their career choice.

Demand and supply working at it's best. Slowly, the tides will turn.

While passion and interest should dictate specialty choice, it doesn't hurt to add appropriate compensation for the work a nephrologist does for the complex patients with tough disease states.

http://www.kidneynews.org/careers/leading-edge/report-shows-increase-in-compensation-for-nephrologists

Sunday, July 24, 2016

Clinical Case 88: Answers and Summary


Which one of these immune check point inhibitors leads to loss of transplanted kidney?


The correct answer is nivolumab or PD-1 inhibitors.  Several cases of kidney injury have now been reported when the immune check point inhibitor use in kidney transplant patients. While Lipson et al had initially reported successful administration of ipilimumab to two kidney transplantation patients with metastatic melanoma without any rejection, they recently reported a case of tumor regression but allograft rejection after administration of   pembrolizumab.  In addition, three cases of rejection were reported with use of nivolumab  in renal transplant patients with melanoma. 
https://www.ncbi.nlm.nih.gov/pubmed/26951628
https://www.ncbi.nlm.nih.gov/pubmed/26988410
Based on the 6 cases, it appears that PD-1 inhibitors are more prone to causing rejection in the transplanted kidney compared to CTLA-4 antagonists , especially when the  patients  have received anti CTLA-4 agents prior to PD-1 inhibitor treatment.  Graft tolerance might be minimized and hence rejection ensues.

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